#!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