1=head1 NAME 2 3perlfaq - frequently asked questions about Perl 4 5=head1 DESCRIPTION 6 7The perlfaq comprises several documents that answer the most commonly 8asked questions about Perl and Perl programming. It's divided by topic 9into nine major sections outlined in this document. 10 11=head2 Where to get the perlfaq 12 13The perlfaq comes with the standard Perl distribution, so if you have Perl 14you should have the perlfaq. You should also have the C<perldoc> tool 15that let's you read the L<perlfaq>: 16 17 $ perldoc perlfaq 18 19Besides your local system, you can find the perlfaq on the web, including 20at http://perldoc.perl.org/ . 21 22The perlfaq is an evolving document and you can read the latest version 23at http://faq.perl.org/ . The perlfaq-workers periodically post extracts 24of the latest perlfaq to comp.lang.perl.misc. 25 26You can view the source tree at 27http://cvs.perl.org/viewcvs/cvs-public/perlfaq/ (which is outside of the 28main Perl source tree). The CVS repository notes all changes to the FAQ 29and holds the latest version of the working documents and may vary 30significantly from the version distributed with the latest version of 31Perl. Check the repository before sending your corrections. 32 33=head2 How to contribute to the perlfaq 34 35You can mail corrections, additions, and suggestions to 36C<< <perlfaq-workers AT perl DOT org> >>. The perlfaq volunteers use this 37address to coordinate their efforts and track the perlfaq development. 38They appreciate your contributions to the FAQ but do not have time to 39provide individual help, so don't use this address to ask FAQs. 40 41The perlfaq server posts extracts of the perlfaq to that newsgroup every 426 hours (or so), and the community of volunteers reviews and updates the 43answers. If you'd like to help review and update the answers, check out 44comp.lang.perl.misc. 45 46=head2 What will happen if you mail your Perl programming problems to the authors? 47 48The perlfaq-workers like to keep all traffic on the perlfaq-workers list 49so that everyone can see the work being done (and the work that needs to 50be done). The mailing list serves as an official record. If you email the 51authors or maintainers directly, you'll probably get a reply asking you 52to post to the mailing list. If you don't get a reply, it probably means 53that the person never saw the message or didn't have time to deal with 54it. Posting to the list allows the volunteers with time to deal with it 55when others are busy. 56 57If you have a question that isn't in the FAQ and you would like help with 58it, try the resources in L<perlfaq2>. 59 60=head1 CREDITS 61 62Tom Christiansen wrote the original perlfaq then expanded it with the 63help of Nat Torkington. The perlfaq-workers maintain current document 64and the dezinens of comp.lang.perl.misc regularly review and update the 65FAQ. Several people have contributed answers, corrections, and comments, 66and the perlfaq notes those contributions wherever appropriate. 67 68=head1 AUTHOR AND COPYRIGHT 69 70Tom Christainsen wrote the original version of this document. 71brian d foy C<< <bdfoy@cpan.org> >> wrote this version. See the 72individual perlfaq documents for additional copyright information. 73 74This document is available under the same terms as Perl itself. Code 75examples in all the perlfaq documents are in the public domain. Use 76them as you see fit (and at your own risk with no warranty from anyone). 77 78=head1 Table of Contents 79 80=over 4 81 82=item perlfaq - this document 83 84=item perlfaq1 - General Questions About Perl 85 86=item perlfaq2 - Obtaining and Learning about Perl 87 88=item perlfaq3 - Programming Tools 89 90=item perlfaq4 - Data Manipulation 91 92=item perlfaq5 - Files and Formats 93 94=item perlfaq6 - Regular Expressions 95 96=item perlfaq7 - General Perl Language Issues 97 98=item perlfaq8 - System Interaction 99 100=item perlfaq9 - Networking 101 102=back 103 104=head1 The Questions 105 106=head2 L<perlfaq1>: General Questions About Perl 107 108Very general, high-level questions about Perl. 109 110=over 4 111 112=item * 113 114What is Perl? 115 116=item * 117 118Who supports Perl? Who develops it? Why is it free? 119 120=item * 121 122Which version of Perl should I use? 123 124=item * 125 126What are perl4, perl5, or perl6? 127 128=item * 129 130What is Ponie? 131 132=item * 133 134What is perl6? 135 136=item * 137 138How stable is Perl? 139 140=item * 141 142Is Perl difficult to learn? 143 144=item * 145 146How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl? 147 148=item * 149 150Can I do [task] in Perl? 151 152=item * 153 154When shouldn't I program in Perl? 155 156=item * 157 158What's the difference between "perl" and "Perl"? 159 160=item * 161 162Is it a Perl program or a Perl script? 163 164=item * 165 166What is a JAPH? 167 168=item * 169 170Where can I get a list of Larry Wall witticisms? 171 172=item * 173 174How can I convince my sysadmin/supervisor/employees to use version 5/5.6.1/Perl instead of some other language? 175 176=back 177 178 179=head2 L<perlfaq2>: Obtaining and Learning about Perl 180 181Where to find source and documentation for Perl, support, and related matters. 182 183=over 4 184 185=item * 186 187What machines support perl? Where do I get it? 188 189=item * 190 191How can I get a binary version of perl? 192 193=item * 194 195I don't have a C compiler. How can I build my own Perl interpreter? 196 197=item * 198 199I copied the perl binary from one machine to another, but scripts don't work. 200 201=item * 202 203I grabbed the sources and tried to compile but gdbm/dynamic loading/malloc/linking/... failed. How do I make it work? 204 205=item * 206 207What modules and extensions are available for Perl? What is CPAN? What does CPAN/src/... mean? 208 209=item * 210 211Is there an ISO or ANSI certified version of Perl? 212 213=item * 214 215Where can I get information on Perl? 216 217=item * 218 219What are the Perl newsgroups on Usenet? Where do I post questions? 220 221=item * 222 223Where should I post source code? 224 225=item * 226 227Perl Books 228 229=item * 230 231Which magazines have Perl content? 232 233=item * 234 235What mailing lists are there for Perl? 236 237=item * 238 239Where are the archives for comp.lang.perl.misc? 240 241=item * 242 243Where can I buy a commercial version of perl? 244 245=item * 246 247Where do I send bug reports? 248 249=item * 250 251What is perl.com? Perl Mongers? pm.org? perl.org? cpan.org? 252 253=back 254 255 256=head2 L<perlfaq3>: Programming Tools 257 258Programmer tools and programming support. 259 260=over 4 261 262=item * 263 264How do I do (anything)? 265 266=item * 267 268How can I use Perl interactively? 269 270=item * 271 272Is there a Perl shell? 273 274=item * 275 276How do I find which modules are installed on my system? 277 278=item * 279 280How do I debug my Perl programs? 281 282=item * 283 284How do I profile my Perl programs? 285 286=item * 287 288How do I cross-reference my Perl programs? 289 290=item * 291 292Is there a pretty-printer (formatter) for Perl? 293 294=item * 295 296Is there a ctags for Perl? 297 298=item * 299 300Is there an IDE or Windows Perl Editor? 301 302=item * 303 304Where can I get Perl macros for vi? 305 306=item * 307 308Where can I get perl-mode for emacs? 309 310=item * 311 312How can I use curses with Perl? 313 314=item * 315 316How can I use X or Tk with Perl? 317 318=item * 319 320How can I make my Perl program run faster? 321 322=item * 323 324How can I make my Perl program take less memory? 325 326=item * 327 328Is it safe to return a reference to local or lexical data? 329 330=item * 331 332How can I free an array or hash so my program shrinks? 333 334=item * 335 336How can I make my CGI script more efficient? 337 338=item * 339 340How can I hide the source for my Perl program? 341 342=item * 343 344How can I compile my Perl program into byte code or C? 345 346=item * 347 348How can I compile Perl into Java? 349 350=item * 351 352How can I get C<#!perl> to work on [MS-DOS,NT,...]? 353 354=item * 355 356Can I write useful Perl programs on the command line? 357 358=item * 359 360Why don't Perl one-liners work on my DOS/Mac/VMS system? 361 362=item * 363 364Where can I learn about CGI or Web programming in Perl? 365 366=item * 367 368Where can I learn about object-oriented Perl programming? 369 370=item * 371 372Where can I learn about linking C with Perl? 373 374=item * 375 376I've read perlembed, perlguts, etc., but I can't embed perl in my C program; what am I doing wrong? 377 378=item * 379 380When I tried to run my script, I got this message. What does it mean? 381 382=item * 383 384What's MakeMaker? 385 386=back 387 388 389=head2 L<perlfaq4>: Data Manipulation 390 391Manipulating numbers, dates, strings, arrays, hashes, and miscellaneous data issues. 392 393=over 4 394 395=item * 396 397Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)? 398 399=item * 400 401Why is int() broken? 402 403=item * 404 405Why isn't my octal data interpreted correctly? 406 407=item * 408 409Does Perl have a round() function? What about ceil() and floor()? Trig functions? 410 411=item * 412 413How do I convert between numeric representations/bases/radixes? 414 415=item * 416 417Why doesn't & work the way I want it to? 418 419=item * 420 421How do I multiply matrices? 422 423=item * 424 425How do I perform an operation on a series of integers? 426 427=item * 428 429How can I output Roman numerals? 430 431=item * 432 433Why aren't my random numbers random? 434 435=item * 436 437How do I get a random number between X and Y? 438 439=item * 440 441How do I find the day or week of the year? 442 443=item * 444 445How do I find the current century or millennium? 446 447=item * 448 449How can I compare two dates and find the difference? 450 451=item * 452 453How can I take a string and turn it into epoch seconds? 454 455=item * 456 457How can I find the Julian Day? 458 459=item * 460 461How do I find yesterday's date? 462 463=item * 464 465Does Perl have a Year 2000 problem? Is Perl Y2K compliant? 466 467=item * 468 469How do I validate input? 470 471=item * 472 473How do I unescape a string? 474 475=item * 476 477How do I remove consecutive pairs of characters? 478 479=item * 480 481How do I expand function calls in a string? 482 483=item * 484 485How do I find matching/nesting anything? 486 487=item * 488 489How do I reverse a string? 490 491=item * 492 493How do I expand tabs in a string? 494 495=item * 496 497How do I reformat a paragraph? 498 499=item * 500 501How can I access or change N characters of a string? 502 503=item * 504 505How do I change the Nth occurrence of something? 506 507=item * 508 509How can I count the number of occurrences of a substring within a string? 510 511=item * 512 513How do I capitalize all the words on one line? 514 515=item * 516 517How can I split a [character] delimited string except when inside [character]? 518 519=item * 520 521How do I strip blank space from the beginning/end of a string? 522 523=item * 524 525How do I pad a string with blanks or pad a number with zeroes? 526 527=item * 528 529How do I extract selected columns from a string? 530 531=item * 532 533How do I find the soundex value of a string? 534 535=item * 536 537How can I expand variables in text strings? 538 539=item * 540 541What's wrong with always quoting "$vars"? 542 543=item * 544 545Why don't my E<lt>E<lt>HERE documents work? 546 547=item * 548 549What is the difference between a list and an array? 550 551=item * 552 553What is the difference between $array[1] and @array[1]? 554 555=item * 556 557How can I remove duplicate elements from a list or array? 558 559=item * 560 561How can I tell whether a certain element is contained in a list or array? 562 563=item * 564 565How do I compute the difference of two arrays? How do I compute the intersection of two arrays? 566 567=item * 568 569How do I test whether two arrays or hashes are equal? 570 571=item * 572 573How do I find the first array element for which a condition is true? 574 575=item * 576 577How do I handle linked lists? 578 579=item * 580 581How do I handle circular lists? 582 583=item * 584 585How do I shuffle an array randomly? 586 587=item * 588 589How do I process/modify each element of an array? 590 591=item * 592 593How do I select a random element from an array? 594 595=item * 596 597How do I permute N elements of a list? 598 599=item * 600 601How do I sort an array by (anything)? 602 603=item * 604 605How do I manipulate arrays of bits? 606 607=item * 608 609Why does defined() return true on empty arrays and hashes? 610 611=item * 612 613How do I process an entire hash? 614 615=item * 616 617What happens if I add or remove keys from a hash while iterating over it? 618 619=item * 620 621How do I look up a hash element by value? 622 623=item * 624 625How can I know how many entries are in a hash? 626 627=item * 628 629How do I sort a hash (optionally by value instead of key)? 630 631=item * 632 633How can I always keep my hash sorted? 634 635=item * 636 637What's the difference between "delete" and "undef" with hashes? 638 639=item * 640 641Why don't my tied hashes make the defined/exists distinction? 642 643=item * 644 645How do I reset an each() operation part-way through? 646 647=item * 648 649How can I get the unique keys from two hashes? 650 651=item * 652 653How can I store a multidimensional array in a DBM file? 654 655=item * 656 657How can I make my hash remember the order I put elements into it? 658 659=item * 660 661Why does passing a subroutine an undefined element in a hash create it? 662 663=item * 664 665How can I make the Perl equivalent of a C structure/C++ class/hash or array of hashes or arrays? 666 667=item * 668 669How can I use a reference as a hash key? 670 671=item * 672 673How do I handle binary data correctly? 674 675=item * 676 677How do I determine whether a scalar is a number/whole/integer/float? 678 679=item * 680 681How do I keep persistent data across program calls? 682 683=item * 684 685How do I print out or copy a recursive data structure? 686 687=item * 688 689How do I define methods for every class/object? 690 691=item * 692 693How do I verify a credit card checksum? 694 695=item * 696 697How do I pack arrays of doubles or floats for XS code? 698 699=back 700 701 702=head2 L<perlfaq5>: Files and Formats 703 704I/O and the "f" issues: filehandles, flushing, formats, and footers. 705 706=over 4 707 708=item * 709 710How do I flush/unbuffer an output filehandle? Why must I do this? 711 712=item * 713 714How 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? 715 716=item * 717 718How do I count the number of lines in a file? 719 720=item * 721 722How can I use Perl's C<-i> option from within a program? 723 724=item * 725 726How can I copy a file? 727 728=item * 729 730How do I make a temporary file name? 731 732=item * 733 734How can I manipulate fixed-record-length files? 735 736=item * 737 738How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles? 739 740=item * 741 742How can I use a filehandle indirectly? 743 744=item * 745 746How can I set up a footer format to be used with write()? 747 748=item * 749 750How can I write() into a string? 751 752=item * 753 754How can I output my numbers with commas added? 755 756=item * 757 758How can I translate tildes (~) in a filename? 759 760=item * 761 762How come when I open a file read-write it wipes it out? 763 764=item * 765 766Why do I sometimes get an "Argument list too long" when I use E<lt>*E<gt>? 767 768=item * 769 770Is there a leak/bug in glob()? 771 772=item * 773 774How can I open a file with a leading ">" or trailing blanks? 775 776=item * 777 778How can I reliably rename a file? 779 780=item * 781 782How can I lock a file? 783 784=item * 785 786Why can't I just open(FH, "E<gt>file.lock")? 787 788=item * 789 790I still don't get locking. I just want to increment the number in the file. How can I do this? 791 792=item * 793 794All I want to do is append a small amount of text to the end of a file. Do I still have to use locking? 795 796=item * 797 798How do I randomly update a binary file? 799 800=item * 801 802How do I get a file's timestamp in perl? 803 804=item * 805 806How do I set a file's timestamp in perl? 807 808=item * 809 810How do I print to more than one file at once? 811 812=item * 813 814How can I read in an entire file all at once? 815 816=item * 817 818How can I read in a file by paragraphs? 819 820=item * 821 822How can I read a single character from a file? From the keyboard? 823 824=item * 825 826How can I tell whether there's a character waiting on a filehandle? 827 828=item * 829 830How do I do a C<tail -f> in perl? 831 832=item * 833 834How do I dup() a filehandle in Perl? 835 836=item * 837 838How do I close a file descriptor by number? 839 840=item * 841 842Why can't I use "C:\temp\foo" in DOS paths? Why doesn't `C:\temp\foo.exe` work? 843 844=item * 845 846Why doesn't glob("*.*") get all the files? 847 848=item * 849 850Why does Perl let me delete read-only files? Why does C<-i> clobber protected files? Isn't this a bug in Perl? 851 852=item * 853 854How do I select a random line from a file? 855 856=item * 857 858Why do I get weird spaces when I print an array of lines? 859 860=back 861 862 863=head2 L<perlfaq6>: Regular Expressions 864 865This section is surprisingly small because the rest of the FAQ is littered with answers involving regular expressions. For example, decoding a URL and checking whether something is a number are handled with regular expressions, but those answers are found elsewhere in this document (in L<perlfaq9>: "How do I decode or create those %-encodings on the web" and L<perlfaq4>: "How do I determine whether a scalar is a number/whole/integer/float", to be precise). 866 867=over 4 868 869=item * 870 871How can I hope to use regular expressions without creating illegible and unmaintainable code? 872 873=item * 874 875I'm having trouble matching over more than one line. What's wrong? 876 877=item * 878 879How can I pull out lines between two patterns that are themselves on different lines? 880 881=item * 882 883I put a regular expression into $/ but it didn't work. What's wrong? 884 885=item * 886 887How do I substitute case insensitively on the LHS while preserving case on the RHS? 888 889=item * 890 891How can I make C<\w> match national character sets? 892 893=item * 894 895How can I match a locale-smart version of C</[a-zA-Z]/>? 896 897=item * 898 899How can I quote a variable to use in a regex? 900 901=item * 902 903What is C</o> really for? 904 905=item * 906 907How do I use a regular expression to strip C style comments from a file? 908 909=item * 910 911Can I use Perl regular expressions to match balanced text? 912 913=item * 914 915What does it mean that regexes are greedy? How can I get around it? 916 917=item * 918 919How do I process each word on each line? 920 921=item * 922 923How can I print out a word-frequency or line-frequency summary? 924 925=item * 926 927How can I do approximate matching? 928 929=item * 930 931How do I efficiently match many regular expressions at once? 932 933=item * 934 935Why don't word-boundary searches with C<\b> work for me? 936 937=item * 938 939Why does using $&, $`, or $' slow my program down? 940 941=item * 942 943What good is C<\G> in a regular expression? 944 945=item * 946 947Are Perl regexes DFAs or NFAs? Are they POSIX compliant? 948 949=item * 950 951What's wrong with using grep in a void context? 952 953=item * 954 955How can I match strings with multibyte characters? 956 957=item * 958 959How do I match a pattern that is supplied by the user? 960 961=back 962 963 964=head2 L<perlfaq7>: General Perl Language Issues 965 966General Perl language issues that don't clearly fit into any of the other sections. 967 968=over 4 969 970=item * 971 972Can I get a BNF/yacc/RE for the Perl language? 973 974=item * 975 976What are all these $@%&* punctuation signs, and how do I know when to use them? 977 978=item * 979 980Do I always/never have to quote my strings or use semicolons and commas? 981 982=item * 983 984How do I skip some return values? 985 986=item * 987 988How do I temporarily block warnings? 989 990=item * 991 992What's an extension? 993 994=item * 995 996Why do Perl operators have different precedence than C operators? 997 998=item * 999 1000How do I declare/create a structure? 1001 1002=item * 1003 1004How do I create a module? 1005 1006=item * 1007 1008How do I create a class? 1009 1010=item * 1011 1012How can I tell if a variable is tainted? 1013 1014=item * 1015 1016What's a closure? 1017 1018=item * 1019 1020What is variable suicide and how can I prevent it? 1021 1022=item * 1023 1024How can I pass/return a {Function, FileHandle, Array, Hash, Method, Regex}? 1025 1026=item * 1027 1028How do I create a static variable? 1029 1030=item * 1031 1032What's the difference between dynamic and lexical (static) scoping? Between local() and my()? 1033 1034=item * 1035 1036How can I access a dynamic variable while a similarly named lexical is in scope? 1037 1038=item * 1039 1040What's the difference between deep and shallow binding? 1041 1042=item * 1043 1044Why doesn't "my($foo) = E<lt>FILEE<gt>;" work right? 1045 1046=item * 1047 1048How do I redefine a builtin function, operator, or method? 1049 1050=item * 1051 1052What's the difference between calling a function as &foo and foo()? 1053 1054=item * 1055 1056How do I create a switch or case statement? 1057 1058=item * 1059 1060How can I catch accesses to undefined variables, functions, or methods? 1061 1062=item * 1063 1064Why can't a method included in this same file be found? 1065 1066=item * 1067 1068How can I find out my current package? 1069 1070=item * 1071 1072How can I comment out a large block of perl code? 1073 1074=item * 1075 1076How do I clear a package? 1077 1078=item * 1079 1080How can I use a variable as a variable name? 1081 1082=item * 1083 1084What does "bad interpreter" mean? 1085 1086=back 1087 1088 1089=head2 L<perlfaq8>: System Interaction 1090 1091This section of the Perl FAQ covers questions involving operating system interaction. Topics include interprocess communication (IPC), control over the user-interface (keyboard, screen and pointing devices), and most anything else not related to data manipulation. Read the FAQs and documentation specific to the port of perl to your operating system (eg, L<perlvms>, L<perlplan9>, ...). These should contain more detailed information on the vagaries of your perl. 1092 1093=over 4 1094 1095=item * 1096 1097How do I find out which operating system I'm running under? 1098 1099=item * 1100 1101How come exec() doesn't return? 1102 1103=item * 1104 1105How do I do fancy stuff with the keyboard/screen/mouse? 1106 1107=item * 1108 1109How do I print something out in color? 1110 1111=item * 1112 1113How do I read just one key without waiting for a return key? 1114 1115=item * 1116 1117How do I check whether input is ready on the keyboard? 1118 1119=item * 1120 1121How do I clear the screen? 1122 1123=item * 1124 1125How do I get the screen size? 1126 1127=item * 1128 1129How do I ask the user for a password? 1130 1131=item * 1132 1133How do I read and write the serial port? 1134 1135=item * 1136 1137How do I decode encrypted password files? 1138 1139=item * 1140 1141How do I start a process in the background? 1142 1143=item * 1144 1145How do I trap control characters/signals? 1146 1147=item * 1148 1149How do I modify the shadow password file on a Unix system? 1150 1151=item * 1152 1153How do I set the time and date? 1154 1155=item * 1156 1157How can I sleep() or alarm() for under a second? 1158 1159=item * 1160 1161How can I measure time under a second? 1162 1163=item * 1164 1165How can I do an atexit() or setjmp()/longjmp()? (Exception handling) 1166 1167=item * 1168 1169Why doesn't my sockets program work under System V (Solaris)? What does the error message "Protocol not supported" mean? 1170 1171=item * 1172 1173How can I call my system's unique C functions from Perl? 1174 1175=item * 1176 1177Where do I get the include files to do ioctl() or syscall()? 1178 1179=item * 1180 1181Why do setuid perl scripts complain about kernel problems? 1182 1183=item * 1184 1185How can I open a pipe both to and from a command? 1186 1187=item * 1188 1189Why can't I get the output of a command with system()? 1190 1191=item * 1192 1193How can I capture STDERR from an external command? 1194 1195=item * 1196 1197Why doesn't open() return an error when a pipe open fails? 1198 1199=item * 1200 1201What's wrong with using backticks in a void context? 1202 1203=item * 1204 1205How can I call backticks without shell processing? 1206 1207=item * 1208 1209Why can't my script read from STDIN after I gave it EOF (^D on Unix, ^Z on MS-DOS)? 1210 1211=item * 1212 1213How can I convert my shell script to perl? 1214 1215=item * 1216 1217Can I use perl to run a telnet or ftp session? 1218 1219=item * 1220 1221How can I write expect in Perl? 1222 1223=item * 1224 1225Is there a way to hide perl's command line from programs such as "ps"? 1226 1227=item * 1228 1229I {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? 1230 1231=item * 1232 1233How do I close a process's filehandle without waiting for it to complete? 1234 1235=item * 1236 1237How do I fork a daemon process? 1238 1239=item * 1240 1241How do I find out if I'm running interactively or not? 1242 1243=item * 1244 1245How do I timeout a slow event? 1246 1247=item * 1248 1249How do I set CPU limits? 1250 1251=item * 1252 1253How do I avoid zombies on a Unix system? 1254 1255=item * 1256 1257How do I use an SQL database? 1258 1259=item * 1260 1261How do I make a system() exit on control-C? 1262 1263=item * 1264 1265How do I open a file without blocking? 1266 1267=item * 1268 1269How do I tell the difference between errors from the shell and perl? 1270 1271=item * 1272 1273How do I install a module from CPAN? 1274 1275=item * 1276 1277What's the difference between require and use? 1278 1279=item * 1280 1281How do I keep my own module/library directory? 1282 1283=item * 1284 1285How do I add the directory my program lives in to the module/library search path? 1286 1287=item * 1288 1289How do I add a directory to my include path (@INC) at runtime? 1290 1291=item * 1292 1293What is socket.ph and where do I get it? 1294 1295=back 1296 1297 1298=head2 L<perlfaq9>: Networking 1299 1300Networking, the internet, and a few on the web. 1301 1302=over 4 1303 1304=item * 1305 1306What is the correct form of response from a CGI script? 1307 1308=item * 1309 1310My CGI script runs from the command line but not the browser. (500 Server Error) 1311 1312=item * 1313 1314How can I get better error messages from a CGI program? 1315 1316=item * 1317 1318How do I remove HTML from a string? 1319 1320=item * 1321 1322How do I extract URLs? 1323 1324=item * 1325 1326How do I download a file from the user's machine? How do I open a file on another machine? 1327 1328=item * 1329 1330How do I make a pop-up menu in HTML? 1331 1332=item * 1333 1334How do I fetch an HTML file? 1335 1336=item * 1337 1338How do I automate an HTML form submission? 1339 1340=item * 1341 1342How do I decode or create those %-encodings on the web? 1343 1344=item * 1345 1346How do I redirect to another page? 1347 1348=item * 1349 1350How do I put a password on my web pages? 1351 1352=item * 1353 1354How do I edit my .htpasswd and .htgroup files with Perl? 1355 1356=item * 1357 1358How do I make sure users can't enter values into a form that cause my CGI script to do bad things? 1359 1360=item * 1361 1362How do I parse a mail header? 1363 1364=item * 1365 1366How do I decode a CGI form? 1367 1368=item * 1369 1370How do I check a valid mail address? 1371 1372=item * 1373 1374How do I decode a MIME/BASE64 string? 1375 1376=item * 1377 1378How do I return the user's mail address? 1379 1380=item * 1381 1382How do I send mail? 1383 1384=item * 1385 1386How do I use MIME to make an attachment to a mail message? 1387 1388=item * 1389 1390How do I read mail? 1391 1392=item * 1393 1394How do I find out my hostname, domainname, or IP address? 1395 1396=item * 1397 1398How do I fetch a news article or the active newsgroups? 1399 1400=item * 1401 1402How do I fetch/put an FTP file? 1403 1404=item * 1405 1406How can I do RPC in Perl? 1407 1408=back 1409 1410 1411