Rightly or wrongly, I use the debugger. I use it all the time to step through code that I have inherited. Along the way I have run across a few debugger idioms that have been invaluable to my code archiology.

Please respond and share your debugger idioms!

• Write intermediate data to a file

In some cases, while debugging, it is helpful to capture an intermediate data structure for reference. I find this particularly useful for dumping out xml content that is generated.

  DB<3> open FH, ">/tmp/foo.txt";
  DB<4> print FH "THIS IS AN EXAMPLE";
  DB<5> print FH $user_id;
  DB<6> close FH
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• Step into an expression

You can evaluate any valid perl expression with x while in the debugger. However you can also step into that expression using s. For example:

  DB<6> s $profile->to_xml()
main::((eval 35)[/usr/lib/perl5/5.6.1/perl5db.pl:1521]:3):
3:      $profile->to_xml();
  DB<<7>>
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At this point, you will be stepping through the expression that was entered on the previous line.

• break the debugger from code

Put the following expression somewhere in your code, run it in the debugger and the debugger will stop on the line immediately following it.

$DB::single = 1;
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There are many more debugger idioms out there, what are yours?