* I completely rewrote the answer to have a friendly tone and actually answer the question. :)
Index: perlfaq3.pod =================================================================== RCS file: /cvs/public/perlfaq/perlfaq3.pod,v retrieving revision 1.56 diff -d -u -r1.56 perlfaq3.pod --- perlfaq3.pod 31 Dec 2005 00:54:37 -0000 1.56 +++ perlfaq3.pod 29 Jan 2006 04:39:47 -0000 @@ -110,28 +110,36 @@ =head2 How do I debug my Perl programs? -Have you tried C<use warnings> or used C<-w>? They enable warnings -to detect dubious practices. +(contributed by brian d foy) -Have you tried C<use strict>? It prevents you from using symbolic -references, makes you predeclare any subroutines that you call as bare -words, and (probably most importantly) forces you to predeclare your -variables with C<my>, C<our>, or C<use vars>. +Before you do anything else, you can help yourself by ensuring that +you let Perl tell you about problem areas in your code. By turning +on warnings and strictures, you can head off many problems before +they get too big. You can find out more about these in L<strict> +and L<warnings>. -Did you check the return values of each and every system call? The operating -system (and thus Perl) tells you whether they worked, and if not -why. + #!/usr/bin/perl + use strict; + use warnings; + +Beyond that, the simplest debugger is the C<print> function. Use it +to look at values as you run your program: - open(FH, "> /etc/cantwrite") - or die "Couldn't write to /etc/cantwrite: $!\n"; + print STDERR "The value is [$value]\n"; -Did you read L<perltrap>? It's full of gotchas for old and new Perl -programmers and even has sections for those of you who are upgrading -from languages like I<awk> and I<C>. +The C<Data::Dumper> module can pretty-print Perl data structures: -Have you tried the Perl debugger, described in L<perldebug>? You can -step through your program and see what it's doing and thus work out -why what it's doing isn't what it should be doing. + use Data::Dumper( Dump ); + print STDERR "The hash is " . Dump( \%hash ) . "\n"; + +Perl comes with an interactive debugger, which you can start with the +C<-d> switch. It's fully explained in L<perldebug>. + +If you'd like a graphical user interface and you have Tk, you can use +C<ptkdb>. It's on CPAN and available for free. + +You can also use a commercial debugger such as Affrus (Mac OS X), Komodo +from Activestate (Windows and Mac OS X), or EPIC (most platforms). =head2 How do I profile my Perl programs?
