1 | =head1 NAME |
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2 | |
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3 | perlfaq - frequently asked questions about Perl ($Date: 2002-02-07 21:12:22 $) |
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4 | |
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5 | =head1 DESCRIPTION |
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6 | |
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7 | The perlfaq is structured into the following documents: |
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8 | |
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9 | |
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10 | =head2 perlfaq: Structural overview of the FAQ. |
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11 | |
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12 | This document. |
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13 | |
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14 | =head2 L<perlfaq1>: General Questions About Perl |
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15 | |
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16 | Very general, high-level information about Perl. |
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17 | |
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18 | =over 4 |
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19 | |
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20 | =item * |
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21 | |
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22 | What is Perl? |
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23 | |
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24 | =item * |
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25 | |
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26 | Who supports Perl? Who develops it? Why is it free? |
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27 | |
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28 | =item * |
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29 | |
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30 | Which version of Perl should I use? |
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31 | |
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32 | =item * |
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33 | |
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34 | What are perl4 and perl5? |
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35 | |
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36 | =item * |
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37 | |
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38 | What is perl6? |
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39 | |
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40 | =item * |
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41 | |
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42 | How stable is Perl? |
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43 | |
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44 | =item * |
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45 | |
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46 | Is Perl difficult to learn? |
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47 | |
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48 | =item * |
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49 | |
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50 | How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl? |
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51 | |
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52 | =item * |
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53 | |
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54 | Can I do [task] in Perl? |
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55 | |
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56 | =item * |
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57 | |
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58 | When shouldn't I program in Perl? |
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59 | |
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60 | =item * |
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61 | |
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62 | What's the difference between "perl" and "Perl"? |
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63 | |
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64 | =item * |
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65 | |
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66 | Is it a Perl program or a Perl script? |
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67 | |
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68 | =item * |
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69 | |
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70 | What is a JAPH? |
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71 | |
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72 | =item * |
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73 | |
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74 | Where can I get a list of Larry Wall witticisms? |
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75 | |
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76 | =item * |
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77 | |
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78 | How can I convince my sysadmin/supervisor/employees to use version 5/5.005/Perl instead of some other language? |
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79 | |
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80 | =back |
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81 | |
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82 | |
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83 | =head2 L<perlfaq2>: Obtaining and Learning about Perl |
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84 | |
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85 | Where to find source and documentation to Perl, support, |
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86 | and related matters. |
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87 | |
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88 | =over 4 |
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89 | |
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90 | =item * |
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91 | |
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92 | What machines support Perl? Where do I get it? |
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93 | |
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94 | =item * |
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95 | |
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96 | How can I get a binary version of Perl? |
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97 | |
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98 | =item * |
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99 | |
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100 | I don't have a C compiler on my system. How can I compile perl? |
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101 | |
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102 | =item * |
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103 | |
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104 | I copied the Perl binary from one machine to another, but scripts don't work. |
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105 | |
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106 | =item * |
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107 | |
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108 | I grabbed the sources and tried to compile but gdbm/dynamic loading/malloc/linking/... failed. How do I make it work? |
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109 | |
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110 | =item * |
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111 | |
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112 | What modules and extensions are available for Perl? What is CPAN? What does CPAN/src/... mean? |
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113 | |
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114 | =item * |
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115 | |
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116 | Is there an ISO or ANSI certified version of Perl? |
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117 | |
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118 | =item * |
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119 | |
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120 | Where can I get information on Perl? |
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121 | |
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122 | =item * |
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123 | |
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124 | What are the Perl newsgroups on Usenet? Where do I post questions? |
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125 | |
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126 | =item * |
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127 | |
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128 | Where should I post source code? |
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129 | |
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130 | =item * |
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131 | |
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132 | Perl Books |
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133 | |
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134 | =item * |
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135 | |
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136 | Perl in Magazines |
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137 | |
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138 | =item * |
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139 | |
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140 | Perl on the Net: FTP and WWW Access |
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141 | |
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142 | =item * |
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143 | |
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144 | What mailing lists are there for Perl? |
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145 | |
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146 | =item * |
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147 | |
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148 | Archives of comp.lang.perl.misc |
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149 | |
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150 | =item * |
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151 | |
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152 | Where can I buy a commercial version of Perl? |
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153 | |
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154 | =item * |
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155 | |
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156 | Where do I send bug reports? |
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157 | |
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158 | =item * |
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159 | |
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160 | What is perl.com? Perl Mongers? pm.org? perl.org? |
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161 | |
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162 | =back |
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163 | |
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164 | |
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165 | =head2 L<perlfaq3>: Programming Tools |
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166 | |
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167 | Programmer tools and programming support. |
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168 | |
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169 | =over 4 |
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170 | |
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171 | =item * |
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172 | |
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173 | How do I do (anything)? |
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174 | |
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175 | =item * |
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176 | |
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177 | How can I use Perl interactively? |
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178 | |
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179 | =item * |
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180 | |
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181 | Is there a Perl shell? |
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182 | |
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183 | =item * |
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184 | |
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185 | How do I debug my Perl programs? |
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186 | |
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187 | =item * |
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188 | |
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189 | How do I profile my Perl programs? |
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190 | |
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191 | =item * |
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192 | |
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193 | How do I cross-reference my Perl programs? |
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194 | |
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195 | =item * |
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196 | |
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197 | Is there a pretty-printer (formatter) for Perl? |
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198 | |
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199 | =item * |
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200 | |
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201 | Is there a ctags for Perl? |
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202 | |
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203 | =item * |
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204 | |
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205 | Is there an IDE or Windows Perl Editor? |
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206 | |
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207 | =item * |
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208 | |
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209 | Where can I get Perl macros for vi? |
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210 | |
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211 | =item * |
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212 | |
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213 | Where can I get perl-mode for emacs? |
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214 | |
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215 | =item * |
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216 | |
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217 | How can I use curses with Perl? |
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218 | |
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219 | =item * |
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220 | |
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221 | How can I use X or Tk with Perl? |
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222 | |
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223 | =item * |
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224 | |
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225 | How can I generate simple menus without using CGI or Tk? |
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226 | |
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227 | =item * |
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228 | |
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229 | What is undump? |
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230 | |
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231 | =item * |
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232 | |
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233 | How can I make my Perl program run faster? |
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234 | |
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235 | =item * |
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236 | |
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237 | How can I make my Perl program take less memory? |
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238 | |
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239 | =item * |
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240 | |
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241 | Is it unsafe to return a pointer to local data? |
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242 | |
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243 | =item * |
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244 | |
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245 | How can I free an array or hash so my program shrinks? |
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246 | |
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247 | =item * |
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248 | |
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249 | How can I make my CGI script more efficient? |
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250 | |
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251 | =item * |
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252 | |
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253 | How can I hide the source for my Perl program? |
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254 | |
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255 | =item * |
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256 | |
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257 | How can I compile my Perl program into byte code or C? |
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258 | |
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259 | =item * |
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260 | |
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261 | How can I compile Perl into Java? |
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262 | |
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263 | =item * |
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264 | |
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265 | How can I get C<#!perl> to work on [MS-DOS,NT,...]? |
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266 | |
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267 | =item * |
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268 | |
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269 | Can I write useful Perl programs on the command line? |
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270 | |
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271 | =item * |
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272 | |
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273 | Why don't Perl one-liners work on my DOS/Mac/VMS system? |
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274 | |
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275 | =item * |
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276 | |
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277 | Where can I learn about CGI or Web programming in Perl? |
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278 | |
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279 | =item * |
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280 | |
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281 | Where can I learn about object-oriented Perl programming? |
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282 | |
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283 | =item * |
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284 | |
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285 | Where can I learn about linking C with Perl? [h2xs, xsubpp] |
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286 | |
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287 | =item * |
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288 | |
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289 | I've read perlembed, perlguts, etc., but I can't embed perl in |
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290 | my C program; what am I doing wrong? |
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291 | |
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292 | =item * |
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293 | |
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294 | When I tried to run my script, I got this message. What does it |
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295 | mean? |
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296 | |
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297 | =item * |
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298 | |
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299 | What's MakeMaker? |
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300 | |
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301 | =back |
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302 | |
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303 | |
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304 | =head2 L<perlfaq4>: Data Manipulation |
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305 | |
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306 | Manipulating numbers, dates, strings, arrays, hashes, and |
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307 | miscellaneous data issues. |
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308 | |
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309 | =over 4 |
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310 | |
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311 | =item * |
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312 | |
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313 | Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)? |
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314 | |
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315 | =item * |
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316 | |
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317 | Why isn't my octal data interpreted correctly? |
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318 | |
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319 | =item * |
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320 | |
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321 | Does Perl have a round() function? What about ceil() and floor()? Trig functions? |
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322 | |
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323 | =item * |
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324 | |
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325 | How do I convert bits into ints? |
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326 | |
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327 | =item * |
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328 | |
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329 | Why doesn't & work the way I want it to? |
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330 | |
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331 | =item * |
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332 | |
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333 | How do I multiply matrices? |
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334 | |
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335 | =item * |
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336 | |
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337 | How do I perform an operation on a series of integers? |
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338 | |
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339 | =item * |
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340 | |
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341 | How can I output Roman numerals? |
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342 | |
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343 | =item * |
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344 | |
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345 | Why aren't my random numbers random? |
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346 | |
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347 | =item * |
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348 | |
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349 | How do I find the week-of-the-year/day-of-the-year? |
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350 | |
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351 | =item * |
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352 | |
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353 | How do I find the current century or millennium? |
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354 | |
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355 | =item * |
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356 | |
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357 | How can I compare two dates and find the difference? |
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358 | |
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359 | =item * |
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360 | |
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361 | How can I take a string and turn it into epoch seconds? |
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362 | |
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363 | =item * |
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364 | |
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365 | How can I find the Julian Day? |
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366 | |
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367 | =item * |
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368 | |
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369 | How do I find yesterday's date? |
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370 | |
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371 | =item * |
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372 | |
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373 | Does Perl have a Year 2000 problem? Is Perl Y2K compliant? |
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374 | |
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375 | =item * |
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376 | |
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377 | How do I validate input? |
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378 | |
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379 | =item * |
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380 | |
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381 | How do I unescape a string? |
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382 | |
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383 | =item * |
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384 | |
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385 | How do I remove consecutive pairs of characters? |
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386 | |
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387 | =item * |
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388 | |
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389 | How do I expand function calls in a string? |
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390 | |
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391 | =item * |
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392 | |
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393 | How do I find matching/nesting anything? |
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394 | |
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395 | =item * |
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396 | |
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397 | How do I reverse a string? |
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398 | |
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399 | =item * |
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400 | |
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401 | How do I expand tabs in a string? |
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402 | |
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403 | =item * |
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404 | |
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405 | How do I reformat a paragraph? |
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406 | |
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407 | =item * |
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408 | |
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409 | How can I access/change the first N letters of a string? |
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410 | |
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411 | =item * |
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412 | |
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413 | How do I change the Nth occurrence of something? |
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414 | |
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415 | =item * |
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416 | |
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417 | How can I count the number of occurrences of a substring within a string? |
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418 | |
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419 | =item * |
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420 | |
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421 | How do I capitalize all the words on one line? |
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422 | |
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423 | =item * |
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424 | |
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425 | How can I split a [character] delimited string except when inside |
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426 | [character]? (Comma-separated files) |
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427 | |
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428 | =item * |
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429 | |
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430 | How do I strip blank space from the beginning/end of a string? |
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431 | |
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432 | =item * |
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433 | |
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434 | How do I pad a string with blanks or pad a number with zeroes? |
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435 | |
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436 | =item * |
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437 | |
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438 | How do I extract selected columns from a string? |
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439 | |
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440 | =item * |
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441 | |
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442 | How do I find the soundex value of a string? |
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443 | |
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444 | =item * |
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445 | |
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446 | How can I expand variables in text strings? |
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447 | |
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448 | =item * |
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449 | |
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450 | What's wrong with always quoting "$vars"? |
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451 | |
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452 | =item * |
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453 | |
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454 | Why don't my <<HERE documents work? |
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455 | |
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456 | =item * |
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457 | |
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458 | What is the difference between a list and an array? |
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459 | |
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460 | =item * |
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461 | |
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462 | What is the difference between $array[1] and @array[1]? |
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463 | |
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464 | =item * |
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465 | |
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466 | How can I remove duplicate elements from a list or array? |
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467 | |
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468 | =item * |
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469 | |
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470 | How can I tell whether a list or array contains a certain element? |
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471 | |
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472 | =item * |
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473 | |
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474 | How do I compute the difference of two arrays? How do I compute the intersection of two arrays? |
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475 | |
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476 | =item * |
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477 | |
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478 | How do I test whether two arrays or hashes are equal? |
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479 | |
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480 | =item * |
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481 | |
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482 | How do I find the first array element for which a condition is true? |
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483 | |
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484 | =item * |
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485 | |
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486 | How do I handle linked lists? |
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487 | |
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488 | =item * |
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489 | |
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490 | How do I handle circular lists? |
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491 | |
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492 | =item * |
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493 | |
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494 | How do I shuffle an array randomly? |
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495 | |
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496 | =item * |
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497 | |
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498 | How do I process/modify each element of an array? |
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499 | |
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500 | =item * |
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501 | |
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502 | How do I select a random element from an array? |
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503 | |
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504 | =item * |
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505 | |
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506 | How do I permute N elements of a list? |
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507 | |
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508 | =item * |
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509 | |
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510 | How do I sort an array by (anything)? |
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511 | |
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512 | =item * |
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513 | |
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514 | How do I manipulate arrays of bits? |
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515 | |
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516 | =item * |
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517 | |
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518 | Why does defined() return true on empty arrays and hashes? |
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519 | |
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520 | =item * |
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521 | |
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522 | How do I process an entire hash? |
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523 | |
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524 | =item * |
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525 | |
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526 | What happens if I add or remove keys from a hash while iterating over it? |
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527 | |
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528 | =item * |
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529 | |
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530 | How do I look up a hash element by value? |
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531 | |
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532 | =item * |
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533 | |
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534 | How can I know how many entries are in a hash? |
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535 | |
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536 | =item * |
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537 | |
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538 | How do I sort a hash (optionally by value instead of key)? |
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539 | |
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540 | =item * |
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541 | |
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542 | How can I always keep my hash sorted? |
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543 | |
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544 | =item * |
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545 | |
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546 | What's the difference between "delete" and "undef" with hashes? |
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547 | |
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548 | =item * |
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549 | |
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550 | Why don't my tied hashes make the defined/exists distinction? |
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551 | |
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552 | =item * |
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553 | |
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554 | How do I reset an each() operation part-way through? |
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555 | |
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556 | =item * |
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557 | |
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558 | How can I get the unique keys from two hashes? |
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559 | |
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560 | =item * |
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561 | |
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562 | How can I store a multidimensional array in a DBM file? |
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563 | |
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564 | =item * |
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565 | |
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566 | How can I make my hash remember the order I put elements into it? |
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567 | |
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568 | =item * |
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569 | |
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570 | Why does passing a subroutine an undefined element in a hash create it? |
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571 | |
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572 | =item * |
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573 | |
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574 | How can I make the Perl equivalent of a C structure/C++ class/hash or array of hashes or arrays? |
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575 | |
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576 | =item * |
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577 | |
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578 | How can I use a reference as a hash key? |
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579 | |
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580 | =item * |
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581 | |
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582 | How do I handle binary data correctly? |
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583 | |
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584 | =item * |
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585 | |
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586 | How do I determine whether a scalar is a number/whole/integer/float? |
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587 | |
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588 | =item * |
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589 | |
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590 | How do I keep persistent data across program calls? |
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591 | |
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592 | =item * |
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593 | |
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594 | How do I print out or copy a recursive data structure? |
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595 | |
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596 | =item * |
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597 | |
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598 | How do I define methods for every class/object? |
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599 | |
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600 | =item * |
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601 | |
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602 | How do I verify a credit card checksum? |
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603 | |
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604 | =item * |
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605 | |
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606 | How do I pack arrays of doubles or floats for XS code? |
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607 | |
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608 | =back |
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609 | |
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610 | |
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611 | =head2 L<perlfaq5>: Files and Formats |
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612 | |
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613 | I/O and the "f" issues: filehandles, flushing, formats and footers. |
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614 | |
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615 | =over 4 |
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616 | |
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617 | =item * |
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618 | |
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619 | How do I flush/unbuffer an output filehandle? Why must I do this? |
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620 | |
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621 | =item * |
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622 | |
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623 | How do I change one line in a file/delete a line in a file/insert a line in the middle of a file/append to the beginning of a file? |
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624 | |
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625 | =item * |
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626 | |
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627 | How do I count the number of lines in a file? |
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628 | |
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629 | =item * |
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630 | |
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631 | How do I make a temporary file name? |
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632 | |
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633 | =item * |
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634 | |
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635 | How can I manipulate fixed-record-length files? |
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636 | |
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637 | =item * |
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638 | |
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639 | How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles? |
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640 | |
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641 | =item * |
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642 | |
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643 | How can I use a filehandle indirectly? |
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644 | |
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645 | =item * |
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646 | |
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647 | How can I set up a footer format to be used with write()? |
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648 | |
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649 | =item * |
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650 | |
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651 | How can I write() into a string? |
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652 | |
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653 | =item * |
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654 | |
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655 | How can I output my numbers with commas added? |
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656 | |
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657 | =item * |
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658 | |
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659 | How can I translate tildes (~) in a filename? |
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660 | |
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661 | =item * |
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662 | |
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663 | How come when I open a file read-write it wipes it out? |
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664 | |
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665 | =item * |
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666 | |
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667 | Why do I sometimes get an "Argument list too long" when I use <*>? |
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668 | |
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669 | =item * |
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670 | |
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671 | Is there a leak/bug in glob()? |
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672 | |
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673 | =item * |
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674 | |
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675 | How can I open a file with a leading ">" or trailing blanks? |
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676 | |
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677 | =item * |
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678 | |
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679 | How can I reliably rename a file? |
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680 | |
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681 | =item * |
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682 | |
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683 | How can I lock a file? |
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684 | |
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685 | =item * |
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686 | |
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687 | Why can't I just open(FH, ">file.lock")? |
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688 | |
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689 | =item * |
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690 | |
---|
691 | I still don't get locking. I just want to increment the number in the file. How can I do this? |
---|
692 | |
---|
693 | =item * |
---|
694 | |
---|
695 | How do I randomly update a binary file? |
---|
696 | |
---|
697 | =item * |
---|
698 | |
---|
699 | How do I get a file's timestamp in perl? |
---|
700 | |
---|
701 | =item * |
---|
702 | |
---|
703 | How do I set a file's timestamp in perl? |
---|
704 | |
---|
705 | =item * |
---|
706 | |
---|
707 | How do I print to more than one file at once? |
---|
708 | |
---|
709 | =item * |
---|
710 | |
---|
711 | How can I read in an entire file all at once? |
---|
712 | |
---|
713 | =item * |
---|
714 | |
---|
715 | How can I read in a file by paragraphs? |
---|
716 | |
---|
717 | =item * |
---|
718 | |
---|
719 | How can I read a single character from a file? From the keyboard? |
---|
720 | |
---|
721 | =item * |
---|
722 | |
---|
723 | How can I tell whether there's a character waiting on a filehandle? |
---|
724 | |
---|
725 | =item * |
---|
726 | |
---|
727 | How do I do a C<tail -f> in perl? |
---|
728 | |
---|
729 | =item * |
---|
730 | |
---|
731 | How do I dup() a filehandle in Perl? |
---|
732 | |
---|
733 | =item * |
---|
734 | |
---|
735 | How do I close a file descriptor by number? |
---|
736 | |
---|
737 | =item * |
---|
738 | |
---|
739 | Why can't I use "C:\temp\foo" in DOS paths? What doesn't `C:\temp\foo.exe` work? |
---|
740 | |
---|
741 | =item * |
---|
742 | |
---|
743 | Why doesn't glob("*.*") get all the files? |
---|
744 | |
---|
745 | =item * |
---|
746 | |
---|
747 | Why does Perl let me delete read-only files? Why does C<-i> clobber protected files? Isn't this a bug in Perl? |
---|
748 | |
---|
749 | =item * |
---|
750 | |
---|
751 | How do I select a random line from a file? |
---|
752 | |
---|
753 | =item * |
---|
754 | |
---|
755 | Why do I get weird spaces when I print an array of lines? |
---|
756 | |
---|
757 | =back |
---|
758 | |
---|
759 | |
---|
760 | =head2 L<perlfaq6>: Regexps |
---|
761 | |
---|
762 | Pattern matching and regular expressions. |
---|
763 | |
---|
764 | =over 4 |
---|
765 | |
---|
766 | =item * |
---|
767 | |
---|
768 | How can I hope to use regular expressions without creating illegible and unmaintainable code? |
---|
769 | |
---|
770 | =item * |
---|
771 | |
---|
772 | I'm having trouble matching over more than one line. What's wrong? |
---|
773 | |
---|
774 | =item * |
---|
775 | |
---|
776 | How can I pull out lines between two patterns that are themselves on different lines? |
---|
777 | |
---|
778 | =item * |
---|
779 | |
---|
780 | I put a regular expression into $/ but it didn't work. What's wrong? |
---|
781 | |
---|
782 | =item * |
---|
783 | |
---|
784 | How do I substitute case insensitively on the LHS while preserving case on the RHS? |
---|
785 | |
---|
786 | =item * |
---|
787 | |
---|
788 | How can I make C<\w> match national character sets? |
---|
789 | |
---|
790 | =item * |
---|
791 | |
---|
792 | How can I match a locale-smart version of C</[a-zA-Z]/>? |
---|
793 | |
---|
794 | =item * |
---|
795 | |
---|
796 | How can I quote a variable to use in a regex? |
---|
797 | |
---|
798 | =item * |
---|
799 | |
---|
800 | What is C</o> really for? |
---|
801 | |
---|
802 | =item * |
---|
803 | |
---|
804 | How do I use a regular expression to strip C style comments from a file? |
---|
805 | |
---|
806 | =item * |
---|
807 | |
---|
808 | Can I use Perl regular expressions to match balanced text? |
---|
809 | |
---|
810 | =item * |
---|
811 | |
---|
812 | What does it mean that regexes are greedy? How can I get around it? |
---|
813 | |
---|
814 | =item * |
---|
815 | |
---|
816 | How do I process each word on each line? |
---|
817 | |
---|
818 | =item * |
---|
819 | |
---|
820 | How can I print out a word-frequency or line-frequency summary? |
---|
821 | |
---|
822 | =item * |
---|
823 | |
---|
824 | How can I do approximate matching? |
---|
825 | |
---|
826 | =item * |
---|
827 | |
---|
828 | How do I efficiently match many regular expressions at once? |
---|
829 | |
---|
830 | =item * |
---|
831 | |
---|
832 | Why don't word-boundary searches with C<\b> work for me? |
---|
833 | |
---|
834 | =item * |
---|
835 | |
---|
836 | Why does using $&, $`, or $' slow my program down? |
---|
837 | |
---|
838 | =item * |
---|
839 | |
---|
840 | What good is C<\G> in a regular expression? |
---|
841 | |
---|
842 | =item * |
---|
843 | |
---|
844 | Are Perl regexes DFAs or NFAs? Are they POSIX compliant? |
---|
845 | |
---|
846 | =item * |
---|
847 | |
---|
848 | What's wrong with using grep or map in a void context? |
---|
849 | |
---|
850 | =item * |
---|
851 | |
---|
852 | How can I match strings with multibyte characters? |
---|
853 | |
---|
854 | =item * |
---|
855 | |
---|
856 | How do I match a pattern that is supplied by the user? |
---|
857 | |
---|
858 | =back |
---|
859 | |
---|
860 | |
---|
861 | =head2 L<perlfaq7>: General Perl Language Issues |
---|
862 | |
---|
863 | General Perl language issues that don't clearly fit into any of the |
---|
864 | other sections. |
---|
865 | |
---|
866 | =over 4 |
---|
867 | |
---|
868 | =item * |
---|
869 | |
---|
870 | Can I get a BNF/yacc/RE for the Perl language? |
---|
871 | |
---|
872 | =item * |
---|
873 | |
---|
874 | What are all these $@%&* punctuation signs, and how do I know when to use them? |
---|
875 | |
---|
876 | =item * |
---|
877 | |
---|
878 | Do I always/never have to quote my strings or use semicolons and commas? |
---|
879 | |
---|
880 | =item * |
---|
881 | |
---|
882 | How do I skip some return values? |
---|
883 | |
---|
884 | =item * |
---|
885 | |
---|
886 | How do I temporarily block warnings? |
---|
887 | |
---|
888 | =item * |
---|
889 | |
---|
890 | What's an extension? |
---|
891 | |
---|
892 | =item * |
---|
893 | |
---|
894 | Why do Perl operators have different precedence than C operators? |
---|
895 | |
---|
896 | =item * |
---|
897 | |
---|
898 | How do I declare/create a structure? |
---|
899 | |
---|
900 | =item * |
---|
901 | |
---|
902 | How do I create a module? |
---|
903 | |
---|
904 | =item * |
---|
905 | |
---|
906 | How do I create a class? |
---|
907 | |
---|
908 | =item * |
---|
909 | |
---|
910 | How can I tell if a variable is tainted? |
---|
911 | |
---|
912 | =item * |
---|
913 | |
---|
914 | What's a closure? |
---|
915 | |
---|
916 | =item * |
---|
917 | |
---|
918 | What is variable suicide and how can I prevent it? |
---|
919 | |
---|
920 | =item * |
---|
921 | |
---|
922 | How can I pass/return a {Function, FileHandle, Array, Hash, Method, Regex}? |
---|
923 | |
---|
924 | =item * |
---|
925 | |
---|
926 | How do I create a static variable? |
---|
927 | |
---|
928 | =item * |
---|
929 | |
---|
930 | What's the difference between dynamic and lexical (static) scoping? Between local() and my()? |
---|
931 | |
---|
932 | =item * |
---|
933 | |
---|
934 | How can I access a dynamic variable while a similarly named lexical is in scope? |
---|
935 | |
---|
936 | =item * |
---|
937 | |
---|
938 | What's the difference between deep and shallow binding? |
---|
939 | |
---|
940 | =item * |
---|
941 | |
---|
942 | Why doesn't "my($foo) = <FILE>;" work right? |
---|
943 | |
---|
944 | =item * |
---|
945 | |
---|
946 | How do I redefine a builtin function, operator, or method? |
---|
947 | |
---|
948 | =item * |
---|
949 | |
---|
950 | What's the difference between calling a function as &foo and foo()? |
---|
951 | |
---|
952 | =item * |
---|
953 | |
---|
954 | How do I create a switch or case statement? |
---|
955 | |
---|
956 | =item * |
---|
957 | |
---|
958 | How can I catch accesses to undefined variables/functions/methods? |
---|
959 | |
---|
960 | =item * |
---|
961 | |
---|
962 | Why can't a method included in this same file be found? |
---|
963 | |
---|
964 | =item * |
---|
965 | |
---|
966 | How can I find out my current package? |
---|
967 | |
---|
968 | =item * |
---|
969 | |
---|
970 | How can I comment out a large block of perl code? |
---|
971 | |
---|
972 | =item * |
---|
973 | |
---|
974 | How do I clear a package? |
---|
975 | |
---|
976 | =item * |
---|
977 | |
---|
978 | How can I use a variable as a variable name? |
---|
979 | |
---|
980 | =back |
---|
981 | |
---|
982 | |
---|
983 | =head2 L<perlfaq8>: System Interaction |
---|
984 | |
---|
985 | Interprocess communication (IPC), control over the user-interface |
---|
986 | (keyboard, screen and pointing devices). |
---|
987 | |
---|
988 | =over 4 |
---|
989 | |
---|
990 | =item * |
---|
991 | |
---|
992 | How do I find out which operating system I'm running under? |
---|
993 | |
---|
994 | =item * |
---|
995 | |
---|
996 | How come exec() doesn't return? |
---|
997 | |
---|
998 | =item * |
---|
999 | |
---|
1000 | How do I do fancy stuff with the keyboard/screen/mouse? |
---|
1001 | |
---|
1002 | =item * |
---|
1003 | |
---|
1004 | How do I print something out in color? |
---|
1005 | |
---|
1006 | =item * |
---|
1007 | |
---|
1008 | How do I read just one key without waiting for a return key? |
---|
1009 | |
---|
1010 | =item * |
---|
1011 | |
---|
1012 | How do I check whether input is ready on the keyboard? |
---|
1013 | |
---|
1014 | =item * |
---|
1015 | |
---|
1016 | How do I clear the screen? |
---|
1017 | |
---|
1018 | =item * |
---|
1019 | |
---|
1020 | How do I get the screen size? |
---|
1021 | |
---|
1022 | =item * |
---|
1023 | |
---|
1024 | How do I ask the user for a password? |
---|
1025 | |
---|
1026 | =item * |
---|
1027 | |
---|
1028 | How do I read and write the serial port? |
---|
1029 | |
---|
1030 | =item * |
---|
1031 | |
---|
1032 | How do I decode encrypted password files? |
---|
1033 | |
---|
1034 | =item * |
---|
1035 | |
---|
1036 | How do I start a process in the background? |
---|
1037 | |
---|
1038 | =item * |
---|
1039 | |
---|
1040 | How do I trap control characters/signals? |
---|
1041 | |
---|
1042 | =item * |
---|
1043 | |
---|
1044 | How do I modify the shadow password file on a Unix system? |
---|
1045 | |
---|
1046 | =item * |
---|
1047 | |
---|
1048 | How do I set the time and date? |
---|
1049 | |
---|
1050 | =item * |
---|
1051 | |
---|
1052 | How can I sleep() or alarm() for under a second? |
---|
1053 | |
---|
1054 | =item * |
---|
1055 | |
---|
1056 | How can I measure time under a second? |
---|
1057 | |
---|
1058 | =item * |
---|
1059 | |
---|
1060 | How can I do an atexit() or setjmp()/longjmp()? (Exception handling) |
---|
1061 | |
---|
1062 | =item * |
---|
1063 | |
---|
1064 | Why doesn't my sockets program work under System V (Solaris)? What does the error message "Protocol not supported" mean? |
---|
1065 | |
---|
1066 | =item * |
---|
1067 | |
---|
1068 | How can I call my system's unique C functions from Perl? |
---|
1069 | |
---|
1070 | =item * |
---|
1071 | |
---|
1072 | Where do I get the include files to do ioctl() or syscall()? |
---|
1073 | |
---|
1074 | =item * |
---|
1075 | |
---|
1076 | Why do setuid perl scripts complain about kernel problems? |
---|
1077 | |
---|
1078 | =item * |
---|
1079 | |
---|
1080 | How can I open a pipe both to and from a command? |
---|
1081 | |
---|
1082 | =item * |
---|
1083 | |
---|
1084 | Why can't I get the output of a command with system()? |
---|
1085 | |
---|
1086 | =item * |
---|
1087 | |
---|
1088 | How can I capture STDERR from an external command? |
---|
1089 | |
---|
1090 | =item * |
---|
1091 | |
---|
1092 | Why doesn't open() return an error when a pipe open fails? |
---|
1093 | |
---|
1094 | =item * |
---|
1095 | |
---|
1096 | What's wrong with using backticks in a void context? |
---|
1097 | |
---|
1098 | =item * |
---|
1099 | |
---|
1100 | How can I call backticks without shell processing? |
---|
1101 | |
---|
1102 | =item * |
---|
1103 | |
---|
1104 | Why can't my script read from STDIN after I gave it EOF (^D on Unix, ^Z on MS-DOS)? |
---|
1105 | |
---|
1106 | =item * |
---|
1107 | |
---|
1108 | How can I convert my shell script to perl? |
---|
1109 | |
---|
1110 | =item * |
---|
1111 | |
---|
1112 | Can I use perl to run a telnet or ftp session? |
---|
1113 | |
---|
1114 | =item * |
---|
1115 | |
---|
1116 | How can I write expect in Perl? |
---|
1117 | |
---|
1118 | =item * |
---|
1119 | |
---|
1120 | Is there a way to hide perl's command line from programs such as "ps"? |
---|
1121 | |
---|
1122 | =item * |
---|
1123 | |
---|
1124 | I {changed directory, modified my environment} in a perl script. How come the change disappeared when I exited the script? How do I get my changes to be visible? |
---|
1125 | |
---|
1126 | =item * |
---|
1127 | |
---|
1128 | How do I close a process's filehandle without waiting for it to complete? |
---|
1129 | |
---|
1130 | =item * |
---|
1131 | |
---|
1132 | How do I fork a daemon process? |
---|
1133 | |
---|
1134 | =item * |
---|
1135 | |
---|
1136 | How do I find out if I'm running interactively or not? |
---|
1137 | |
---|
1138 | =item * |
---|
1139 | |
---|
1140 | How do I timeout a slow event? |
---|
1141 | |
---|
1142 | =item * |
---|
1143 | |
---|
1144 | How do I set CPU limits? |
---|
1145 | |
---|
1146 | =item * |
---|
1147 | |
---|
1148 | How do I avoid zombies on a Unix system? |
---|
1149 | |
---|
1150 | =item * |
---|
1151 | |
---|
1152 | How do I use an SQL database? |
---|
1153 | |
---|
1154 | =item * |
---|
1155 | |
---|
1156 | How do I make a system() exit on control-C? |
---|
1157 | |
---|
1158 | =item * |
---|
1159 | |
---|
1160 | How do I open a file without blocking? |
---|
1161 | |
---|
1162 | =item * |
---|
1163 | |
---|
1164 | How do I install a module from CPAN? |
---|
1165 | |
---|
1166 | =item * |
---|
1167 | |
---|
1168 | What's the difference between require and use? |
---|
1169 | |
---|
1170 | =item * |
---|
1171 | |
---|
1172 | How do I keep my own module/library directory? |
---|
1173 | |
---|
1174 | =item * |
---|
1175 | |
---|
1176 | How do I add the directory my program lives in to the module/library search path? |
---|
1177 | |
---|
1178 | =item * |
---|
1179 | |
---|
1180 | How do I add a directory to my include path at runtime? |
---|
1181 | |
---|
1182 | =item * |
---|
1183 | |
---|
1184 | What is socket.ph and where do I get it? |
---|
1185 | |
---|
1186 | =back |
---|
1187 | |
---|
1188 | |
---|
1189 | =head2 L<perlfaq9>: Networking |
---|
1190 | |
---|
1191 | Networking, the Internet, and a few on the web. |
---|
1192 | |
---|
1193 | =over 4 |
---|
1194 | |
---|
1195 | =item * |
---|
1196 | |
---|
1197 | My CGI script runs from the command line but not the browser. (500 Server Error) |
---|
1198 | |
---|
1199 | =item * |
---|
1200 | |
---|
1201 | How can I get better error messages from a CGI program? |
---|
1202 | |
---|
1203 | =item * |
---|
1204 | |
---|
1205 | How do I remove HTML from a string? |
---|
1206 | |
---|
1207 | =item * |
---|
1208 | |
---|
1209 | How do I extract URLs? |
---|
1210 | |
---|
1211 | =item * |
---|
1212 | |
---|
1213 | How do I download a file from the user's machine? How do I open a file on another machine? |
---|
1214 | |
---|
1215 | =item * |
---|
1216 | |
---|
1217 | How do I make a pop-up menu in HTML? |
---|
1218 | |
---|
1219 | =item * |
---|
1220 | |
---|
1221 | How do I fetch an HTML file? |
---|
1222 | |
---|
1223 | =item * |
---|
1224 | |
---|
1225 | How do I automate an HTML form submission? |
---|
1226 | |
---|
1227 | =item * |
---|
1228 | |
---|
1229 | How do I decode or create those %-encodings on the web? |
---|
1230 | |
---|
1231 | =item * |
---|
1232 | |
---|
1233 | How do I redirect to another page? |
---|
1234 | |
---|
1235 | =item * |
---|
1236 | |
---|
1237 | How do I put a password on my web pages? |
---|
1238 | |
---|
1239 | =item * |
---|
1240 | |
---|
1241 | How do I edit my .htpasswd and .htgroup files with Perl? |
---|
1242 | |
---|
1243 | =item * |
---|
1244 | |
---|
1245 | How do I make sure users can't enter values into a form that cause my CGI script to do bad things? |
---|
1246 | |
---|
1247 | =item * |
---|
1248 | |
---|
1249 | How do I parse a mail header? |
---|
1250 | |
---|
1251 | =item * |
---|
1252 | |
---|
1253 | How do I decode a CGI form? |
---|
1254 | |
---|
1255 | =item * |
---|
1256 | |
---|
1257 | How do I check a valid mail address? |
---|
1258 | |
---|
1259 | =item * |
---|
1260 | |
---|
1261 | How do I decode a MIME/BASE64 string? |
---|
1262 | |
---|
1263 | =item * |
---|
1264 | |
---|
1265 | How do I return the user's mail address? |
---|
1266 | |
---|
1267 | =item * |
---|
1268 | |
---|
1269 | How do I send mail? |
---|
1270 | |
---|
1271 | =item * |
---|
1272 | |
---|
1273 | How do I read mail? |
---|
1274 | |
---|
1275 | =item * |
---|
1276 | |
---|
1277 | How do I find out my hostname/domainname/IP address? |
---|
1278 | |
---|
1279 | =item * |
---|
1280 | |
---|
1281 | How do I fetch a news article or the active newsgroups? |
---|
1282 | |
---|
1283 | =item * |
---|
1284 | |
---|
1285 | How do I fetch/put an FTP file? |
---|
1286 | |
---|
1287 | =item * |
---|
1288 | |
---|
1289 | How can I do RPC in Perl? |
---|
1290 | |
---|
1291 | =back |
---|
1292 | |
---|
1293 | |
---|
1294 | =head1 About the perlfaq documents |
---|
1295 | |
---|
1296 | =head2 Where to get the perlfaq |
---|
1297 | |
---|
1298 | This document is posted regularly to comp.lang.perl.announce and |
---|
1299 | several other related newsgroups. It is available in a variety of |
---|
1300 | formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory or on the web |
---|
1301 | at http://www.perl.com/perl/faq/ . |
---|
1302 | |
---|
1303 | =head2 How to contribute to the perlfaq |
---|
1304 | |
---|
1305 | You may mail corrections, additions, and suggestions to |
---|
1306 | perlfaq-suggestions@perl.com . This alias should not be |
---|
1307 | used to I<ask> FAQs. It's for fixing the current FAQ. |
---|
1308 | Send questions to the comp.lang.perl.misc newsgroup. |
---|
1309 | |
---|
1310 | =head2 What will happen if you mail your Perl programming problems to the authors |
---|
1311 | |
---|
1312 | Your questions will probably go unread, unless they're suggestions of |
---|
1313 | new questions to add to the FAQ, in which case they should have gone |
---|
1314 | to the perlfaq-suggestions@perl.com instead. |
---|
1315 | |
---|
1316 | You should have read section 2 of this faq. There you would have |
---|
1317 | learned that comp.lang.perl.misc is the appropriate place to go for |
---|
1318 | free advice. If your question is really important and you require a |
---|
1319 | prompt and correct answer, you should hire a consultant. |
---|
1320 | |
---|
1321 | =head1 Credits |
---|
1322 | |
---|
1323 | When I first began the Perl FAQ in the late 80s, I never realized it |
---|
1324 | would have grown to over a hundred pages, nor that Perl would ever become |
---|
1325 | so popular and widespread. This document could not have been written |
---|
1326 | without the tremendous help provided by Larry Wall and the rest of the |
---|
1327 | Perl Porters. |
---|
1328 | |
---|
1329 | =head1 Author and Copyright Information |
---|
1330 | |
---|
1331 | Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington. |
---|
1332 | All rights reserved. |
---|
1333 | |
---|
1334 | =head2 Bundled Distributions |
---|
1335 | |
---|
1336 | When included as part of the Standard Version of Perl or as part of |
---|
1337 | its complete documentation whether printed or otherwise, this work |
---|
1338 | may be distributed only under the terms of Perl's Artistic License. |
---|
1339 | Any distribution of this file or derivatives thereof I<outside> |
---|
1340 | of that package requires that special arrangements be made with |
---|
1341 | copyright holder. |
---|
1342 | |
---|
1343 | Irrespective of its distribution, all code examples in these files |
---|
1344 | are hereby placed into the public domain. You are permitted and |
---|
1345 | encouraged to use this code in your own programs for fun |
---|
1346 | or for profit as you see fit. A simple comment in the code giving |
---|
1347 | credit would be courteous but is not required. |
---|
1348 | |
---|
1349 | =head2 Disclaimer |
---|
1350 | |
---|
1351 | This information is offered in good faith and in the hope that it may |
---|
1352 | be of use, but is not guaranteed to be correct, up to date, or suitable |
---|
1353 | for any particular purpose whatsoever. The authors accept no liability |
---|
1354 | in respect of this information or its use. |
---|
1355 | |
---|
1356 | =head1 Changes |
---|
1357 | |
---|
1358 | =over 4 |
---|
1359 | |
---|
1360 | =item 1/November/2000 |
---|
1361 | |
---|
1362 | A few grammatical fixes and updates implemented by John Borwick. |
---|
1363 | |
---|
1364 | =item 23/May/99 |
---|
1365 | |
---|
1366 | Extensive updates from the net in preparation for 5.6 release. |
---|
1367 | |
---|
1368 | =item 13/April/99 |
---|
1369 | |
---|
1370 | More minor touch-ups. Added new question at the end |
---|
1371 | of perlfaq7 on variable names within variables. |
---|
1372 | |
---|
1373 | =item 7/January/99 |
---|
1374 | |
---|
1375 | Small touchups here and there. Added all questions in this |
---|
1376 | document as a sort of table of contents. |
---|
1377 | |
---|
1378 | =item 22/June/98 |
---|
1379 | |
---|
1380 | Significant changes throughout in preparation for the 5.005 |
---|
1381 | release. |
---|
1382 | |
---|
1383 | =item 24/April/97 |
---|
1384 | |
---|
1385 | Style and whitespace changes from Chip, new question on reading one |
---|
1386 | character at a time from a terminal using POSIX from Tom. |
---|
1387 | |
---|
1388 | =item 23/April/97 |
---|
1389 | |
---|
1390 | Added http://www.oasis.leo.org/perl/ to L<perlfaq2>. Style fix to |
---|
1391 | L<perlfaq3>. Added floating point precision, fixed complex number |
---|
1392 | arithmetic, cross-references, caveat for Text::Wrap, alternative |
---|
1393 | answer for initial capitalizing, fixed incorrect regexp, added example |
---|
1394 | of Tie::IxHash to L<perlfaq4>. Added example of passing and storing |
---|
1395 | filehandles, added commify to L<perlfaq5>. Restored variable suicide, |
---|
1396 | and added mass commenting to L<perlfaq7>. Added Net::Telnet, fixed |
---|
1397 | backticks, added reader/writer pair to telnet question, added FindBin, |
---|
1398 | grouped module questions together in L<perlfaq8>. Expanded caveats |
---|
1399 | for the simple URL extractor, gave LWP example, added CGI security |
---|
1400 | question, expanded on the mail address answer in L<perlfaq9>. |
---|
1401 | |
---|
1402 | =item 25/March/97 |
---|
1403 | |
---|
1404 | Added more info to the binary distribution section of L<perlfaq2>. |
---|
1405 | Added Net::Telnet to L<perlfaq6>. Fixed typos in L<perlfaq8>. Added |
---|
1406 | mail sending example to L<perlfaq9>. Added Merlyn's columns to |
---|
1407 | L<perlfaq2>. |
---|
1408 | |
---|
1409 | =item 18/March/97 |
---|
1410 | |
---|
1411 | Added the DATE to the NAME section, indicating which sections have |
---|
1412 | changed. |
---|
1413 | |
---|
1414 | Mentioned SIGPIPE and L<perlipc> in the forking open answer in |
---|
1415 | L<perlfaq8>. |
---|
1416 | |
---|
1417 | Fixed description of a regular expression in L<perlfaq4>. |
---|
1418 | |
---|
1419 | =item 17/March/97 Version |
---|
1420 | |
---|
1421 | Various typos fixed throughout. |
---|
1422 | |
---|
1423 | Added new question on Perl BNF on L<perlfaq7>. |
---|
1424 | |
---|
1425 | =item Initial Release: 11/March/97 |
---|
1426 | |
---|
1427 | This is the initial release of version 3 of the FAQ; consequently there |
---|
1428 | have been no changes since its initial release. |
---|
1429 | |
---|
1430 | =back |
---|