I have used these simple subs many times to great effect. I put them in a "standard utility module" that I use in many programs. I recommend just setting these short subs to return a string, don't use values in main calling program to separate things out. Perhaps these things should/could be called iwascalledby() hewascalledby(); or whatever suits your fancy.

#!usr/bin/perl -w
use strict;

sub whoami  { (caller(1))[3] };  
sub whowasi { (caller(2))[3] };  

some_sub();
sub some_sub
{
  print "Now inside some_sub\n";
  print "  called_by ". whoami.".\n";
  another_sub();
}

sub another_sub
{
  print "Now inside another_sub\n";
  print "  called by ". whoami(). " \n";
  print "  previous sub ". whowasi(). " \n";
}
__END__
Prints:
Now inside some_sub
  called_by main::some_sub.
Now inside another_sub
  called by main::another_sub 
  previous sub main::some_sub
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caller() has more params and they can be useful, eg. line number etc. But basically if one of my library routines gets bogus input, then I usually just need to know the name of the caller and the name of previous caller to figure out where bogus input came from.