Mastering Perl, 2nd Edition

Chapter 3. Perl Debuggers

The standard Perl distribution comes with a debugger, although it’s really just another Perl program, perl5db.pl. Since it is just a program, I can use it as the basis for writing my own debuggers to suit my needs, or I can use the interface perl5db.pl provides to configure its actions. That’s just the beginning, though. I can write my own debugger or use one of the many debuggers created by other Perl masters.

This chapter isn’t about actually debugging Perl source code to find problems; people have written entire books about that. The more you practice Perl, the better you should get at that.

Before You Waste Too Much Time

Before I get started, I’m almost required to remind you that Perl offers two huge debugging aids: strict and warnings. I have the most trouble with smaller programs where I don’t think I need strict and I make the stupid mistakes it would have caught. I spend much more time than I should tracking down something Perl would have shown me instantly. It’s the common mistakes that seem to be the hardest for me to debug. Learn from the master: don’t discount strict or warnings for even small programs.

Now that I’ve said that, you’re going to look for it in the examples in this chapter. Just pretend those lines are there, and the book costs a bit less for the extra half a page that I saved by omitting those lines. Or, if you don’t like that, just imagine that I’m running every program with both strict and warnings turned on from the command line: ...