What are some good Perl debugging methods?

Question

Are there other ways for debugging Perl programs apart from Data::Dumper and perl -d?

Answer 1

I like Devel::Trace. Basically it gives you an execution dump, showing you the code paths.

On another side, test-driven development is all the rage now, so you could also be interested in profiling tools like Devel::NYTProf for highly advanced testing. See this Tim Bunce's blog post for an interesting overview.

Answer 2

Available tools for debugging

There are several tools available in Perl for debugging and similar tasks.

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Built-in command line debugger.

perl -d yourcode.pl

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Devel::ptkdb

Perl/Tk based graphical debugger by Andrew E. Page.

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Regex Coach

This a free tool running both on Linux and Windows written in Lisp. Source code is not available.

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Rx: A Regex Debugger for Perl

The Perl Regex debugger and an article about it written by Mark Jason Dominus.

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A GUI for the Perl Debugger

Answer 3

My usual range of tools is:

• print statements and Data::Dumper for simple cases
• perl -d

That's usually enough. There is ffffd; I heard it's quite nice, but never played with it.

For some tasks (which are not really debugging, but close to it) I use Devel::NYTProf.

Answer 4

I use ActiveState Komodo for step-by-step debugging.

Eclipse has a step by step debugger for its EPIC plugin.

Personally I prefer the ActiveState version. It just seems more solid and stable, but it does cost (and work is paying for me). If it was my money then I would use Eclipse and EPIC as these are free.

Answer 5

The best debugging aids are small routines, short scopes, limited side effects, and lots of tests. Stop bugs before they hatch.

Answer 6

During development, I like to embed printf statements in strategic places (not too many) which are enabled with a debug flag like this:

printf("h='$h', j='$j', ... (%d)\n", __LINE__) if $debug;

where the debug flag is defined at the top of the script:

my $debug = $ENV{DEBUG} || 0;

Now instead of having to remember to comment out all of the printf lines, I just run the script as follows:

DEBUG=1 ./script.pl

After testing when everything is ready for production, the debug lines can be removed:

cat script.pl | grep -v 'if $debug;'