Thanks to you all monks, named or unnamed ones.
I putted the pieces togheter and this was the result (ugly code I know, the command parsing over other things):

#!perl
use strict;
use warnings;
use if ($^O eq 'MSWin32'), 'Win32::Getppid';

my $parent;
my $invoker;


BEGIN{
  if ($^O eq 'MSWin32') {
      $parent = getppid;
      open my $cmd,"tasklist  /nh /FI \"PID eq $parent\" |" or die;
      while (<$cmd>){
            chomp;
            next if /^$/;# yes it outputs a leading empty line..
            $invoker = $1 if /^([\w\d\.]+)\W/;
      }
  }
  else {
       $parent = getppid;
       open my $cmd,"ps -p $parent|" or die;
       while (<$cmd>){
            chomp;
            next if /^[\sA-Z]+$/;# get rid of heaader: freebsd does no
+t support no header output
            $invoker = $1 if /\s([\w\d\.]+)$/;
       }
  }
}


print "Perl (PID $$) was invoked from PID $parent ($invoker)\n";
[download]

It outputs the correct thing in 3 different test cases:

cmd.exe>perl who_called_Perl.pl
Perl (PID 17400) was invoked from PID 10576 (cmd.exe)

powershell> perl.exe who_called_Perl.pl
Perl (PID 18212) was invoked from PID 11272 (powershell.exe)

bash$ perl who_called_perl.pl 
Perl (PID 73288) was invoked from PID 31994 (bash)
[download]

L*