#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use POSIX qw(getpid);  #update for Perl 5.14.1

##########################################################
# you can put it in your development programs like this:
# my $memmonitor = 1;
#  if($memmonitor){
#  my $pid = $$;
#    if(fork() == 0){exec("./memmonitor $pid")}
# }
######################################################


#my $pid = shift || $$;
my $pid = getpid();

my $mw = new MainWindow;
$mw->overrideredirect(1);
my $t = $mw->Label(-text=>'', -bg=>'black', -fg=>'yellow')->pack;

my $id = Tk::After->new($mw,1000,'repeat',\&refresh);

MainLoop;

sub refresh{
      my @size = split "\n", `cat /proc/$pid/status`;
      (my $vmsize) = grep {/VmSize/} @size;
      my (undef,$size) = split "\t",$vmsize;
      $t->configure(-text=>"PID: $pid ->  $size");
      if($size eq ''){Tk::exit}
}
__END__
#################################################

Here is a modular version, save the file below as MeM.pm
package MeM;
use warnings;
use strict;
use POSIX qw(getpid);

#my $pid =$$;
my $pid = getpid();

if (fork() == 0) {
    require Tk;
    my $mw = new MainWindow;
    $mw->overrideredirect(1);
    $mw->geometry('-0-0');
    my $t = $mw->Label(-text => '', -bg => 'black', -fg => 'yellow')->pack;
    $0 = 'MeM';
    my $id = Tk::After->new($mw, 1000, 'repeat', [ \&refresh, $pid ]);

    Tk::MainLoop();

    sub refresh {
        my $pid = shift;
        #asmutils version of cat 
       # my @size = split "\n", `/home/zentara/perl5lib/cat /proc/$pid/status`;
        my @size = split "\n", `cat /proc/$pid/status`; 

        (my $vmsize) = grep { /VmSize/ } @size;
        my (undef, $size) = split '   ', $vmsize;
        $t->configure(-text => "PID: $pid ->  $size");
        if ($size eq '') { exit }
    }
}

1;