Perl FAQ

They're all good questions, but they come up often enough that substantial net bandwidth can be saved by looking here first before asking. Before posting a question, you really should consult the Perl man page; there's a lot of information packed in there.

Some questions in this group aren't really about Perl, but rather about system-specific issues. You might also consult the Most Frequently Asked Questions list in comp.unix.questions for answers to this type of question.

The current version of perl is 4.036 (version 4, patchlevel 35). There haven't actually been 36 updates to perl4; rather, the context diffs posted to the net have been broken up into 36 news-digestable chunks. The 2nd alpha version of version 5.0 perl is available: vide infra.

This list is maintained by Tom Christiansen, and is archived on convex.com [130.168.1.1] in the file pub/perl/info/faq, as well as on rtfm.mit.edu [18.70.0.224] in /pub/usenet/comp.lang.perl . If you have any suggested additions or corrections to this article, please send them to Tom at either <tchrist@cs.colorado.edu> or <tchrist@usenix.org> . Special thanks to Larry Wall for periodically reviewing this list for accuracy and especially for writing and releasing Perl in the first place.

The following questions are answered in part 1:

• 1.1: What is Perl?
• 1.2: Is Perl hard to learn?
• 1.3: Should I program everything in Perl?
• 1.4: Where can I get Perl over the Internet?
• 1.5: Where can I get Perl via Email?
• 1.6: How can I get Perl via UUCP?
• 1.7: Where can I get more information on Perl?
• 1.8: Can people who aren't on USENET receive comp.lang.perl as a digest?
• 1.9: Are archives of comp.lang.perl available?
• 1.10: Is there a WAIS server for Perl?
• 1.11: Is there a Perl port to machine FOO?
• 1.12: How do I get Perl to compile on Solaris?
• 1.13: How do I get Perl to compile on a Next?
• 1.14: Where can I get (info|inter|ora|sql|syb)perl?
• 1.15: Where can I get an SNMP-aware Perl?
• 1.16: There's an a2p and an s2p; why isn't there a p2c (perl-to-C)?
• 1.17: Where can I get undump for my machine?
• 1.18: Where can I get a perl-mode for emacs?
• 1.19: How can I use Perl interactively?
• 1.20: Is there a Perl shell?

• 1.21: Is there a Perl profiler?
• 1.22: Is there a yacc for Perl?
• 1.23: How can I use curses with perl?
• 1.24: How can I use X with Perl?
• 1.25: What is perl4? What is perl5?
• 1.26: How does Perl compare with languages like REXX or TCL?
• 1.27: Is it a Perl program or a Perl script?
• 1.28: What's the difference between "Perl" and "perl"?
• 1.29: What companies use or ship Perl?
• 1.30: Is there commercial, 3rd-party support for Perl?
• 1.31: Where can I get a list of the JAPH signature quotes?
• 1.32: Where can I get a list of Larry Wall witticisms?
• 1.33: Is there a pretty-printer for Perl?
• 1.34: Can I dynamically load C user routines?

• 2.1: What are all these $@*%<> signs and how do I know when to use them?
• 2.2: Why don't backticks work as they do in shells?
• 2.3: How come Perl operators have different precedence than C operators?
• 2.4: How come my converted awk/sed/sh script runs more slowly in Perl?
• 2.5: How can I call my system's unique C functions from Perl?
• 2.6: Where do I get the include files to do ioctl() or syscall()?
• 2.7: Why doesn't "local($foo) = <FILE>;" work right?
• 2.8: How can I detect keyboard input without reading it,
• 2.9: how can I read a single character from the keyboard under UNIX and DOS?
• 2.10: How can I make an array of arrays or other recursive data types?
• 2.11: How do I make an array of structures containing various data types?
• 2.12: How can I quote a variable to use in a regexp?
• 2.13: Why do setuid Perl scripts complain about kernel problems?
• 2.14: How do I open a pipe both to and from a command?
• 2.15: How can I change the first N letters of a string?
• 2.16: How can I manipulate fixed-record-length files?
• 2.17: How can I make a file handle local to a subroutine?
• 2.18: How can I extract just the unique elements of an array?
• 2.19: How can I call alarm() or usleep() from Perl?
• 2.20: How can I test whether an array contains a certain element?
• 2.21: How can I do an atexit() or setjmp()/longjmp() in Perl?
• 2.22: Why doesn't Perl interpret my octal data octally?
• 2.23: How do I sort an associative array by value instead of by key?
• 2.24: How can I capture STDERR from an external command?
• 2.25: Why doesn't open return an error when a pipe open fails?
• 2.26: How can I compare two date strings?
• 2.27: What's the fastest way to code up a given task in perl?
• 2.28: How can I know how many entries are in an associative array?

• 2.29: Why can't my perl program read from STDIN after I gave it ^D (EOF) ?
• 2.30: Do I always/never have to quote my strings or use semicolons?
• 2.31: How can I translate tildes in a filename?
• 2.32: How can I convert my shell script to Perl?
• 2.33: What is variable suicide and how can I prevent it?
• 2.34: Can I use Perl regular expressions to match balanced text?
• 2.35: Can I use Perl to run a telnet or ftp session?
• 2.36: What does "Malformed command links" mean?
• 2.37: How can I set up a footer format to be used with write()?
• 2.38: Why does my Perl program keep growing in size?
• 2.39: Can I do RPC in Perl?
• 2.40: What's the difference between delete and undef with %tables?
• 2.41: How do I do a "tail -f" in Perl?

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      Tom Christiansen      tchrist@cs.colorado.edu       
                      Consultant
          Boulder Colorado  303-444-3212