You would like to use the debuger on programb.pl, if I understand correctly. I doubt it is possible, as the backticks are forking a different process.

But calling a Perl program from another Perl program is somewhat uncommon (although I admit that I have done it a few times, but for very specific reasons) and suggests that there may be an easier way to do it. May be you can put the content of programb.pl into a module and call the right functions of this module. If you do that, you'll be able to enter in debug mode in the functions of the module. I can't tell more, not knowing what your programs are doing and the reasons you decided to use separate Perl programs.

Update: Note that you can redirect STDERR of your forked process into a file, to see any error message printed to standard error. Something like this:

my @result = `perl programb.pl -option 2>error.txt`;
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