How to set breakpoint on a particular file in Perl program?

Question

My Perl program looks like:

foo/
foo/bar/
for/bar/test.pm
foo.pm
foo/bar.pm
test.pl

and use perl test.pl to start the program. I

Answer 1

To debug a perl script, use the -d switch to invoke the debugger.

perl -d test.pl

Within the debugger you can use b <line no> to set a breakpoint in the current file. Sometimes it is a hassle to set a breakpoint in a file that hasn't been loaded yet or that was loaded a long time ago, so you can also put the line

$DB::single = 1;

anywhere in any perl program, and the debugger will break immediately after it executes that line. This is also a good way (the only way?) to set a breakpoint in code that will be run at compile time.

Answer 2

Just use the fully qualified name of the sub as the argument to b:

b foo::bar::test::subname

Example:

$ perl -d -e'use CGI; CGI->new'
...
main::(-e:1):   use CGI; CGI->new
  DB<1> b CGI::new
  DB<2> r
CGI::new(.../CGI.pm:337):
337:      my($class,@initializer) = @_;
  DB<2> q