Hello Ken, seems that the problem is in fact with system() I've tried with

#my @command = ("su - $user -c id")  
####################################
#system ("su - $user"); #this Works#
####################################
#system ("@command") == 0 or die "system @command failed: $?";
#exec ('su - $user -c $action')   or print STDERR "couldn't exec foo: 
+$!";
#exec("/bin/su","-",$user,$action);
#system ("su", "-", $user, "-c", "/bin/bash -c $action");
#system ("su - $user -c /bin/bash -c $action");
#system "sudo","su","-" => $user, -c =>  $action;
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but each one fails!!

also i tried these modules, same result ..

use warnings;
use diagnostics;
use strict;
use Shell::Source;
use Shell;
my $action="\'Anything\'";
my $user="RealUser";
my $sh = Shell->new;
say "$user";
say "$action ";
print $sh->sudo("su -l - $user --command $action");
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I start to thinking if my Gentoo has problems , I'll try in another system...

btw I've checked for $user seems that is good, just before function.

thanks..