Product instance full path
 /opt/wheredb2/Version

Current instance 
Userid

##</code><code>##

use warnings;
use diagnostics;
use strict;
use 5.010;
use Cwd;
use DB2::Admin::Constants;
##############################                                                                                                                                                                                                                                                                                                 
###Get Version and instances##                                                                                                                                                                                                                                                                                                 
##############################                                                                                                                                                                                                                                                                                                 
sub check_for_instance{
  open(EXEC, '-|', 'db2ls | awk	\'!/Install/ &&	!/----/	\'') or	die "Can't exec: $!\n";
  # Now read the output just like a file                                                                                                                                                                                                                                                                                       
  while(my $line = <EXEC>) {
    chomp $line;
    if($line=~/(\/db2\/V\d.\d+)/){
      print "Product instance full path\n $`"."$1\n";
      foreach ($line)
        {
          my $Path="$`"."$1"."/instance/";
	  chdir($Path) or die "Cant chdir to $Path $!";
          my $dir = getcwd;
          open my $cmd,	'-|', './db2ilist';
          while ($line = <$cmd>) {
	    say	"Current instance \n$line";
	    my $user="$line"; my $action="db2 list db directory";
#########################
###  This doesn't works #
#########################
	    system ("su	-l - $user -c \'$action	> DBlist.txt && cat  DBlist.txt\'");

###########################
#                         #
#   this works ! XD       #
###########################
#system ("su -l - MyRealuser -c \'$action > DBlist.txt && cat  DBlist.txt\'");
#######
          }
          close $cmd;
	}
    }
  }
  close(EXEC);
}
&check_for_instance;