#!/usr/bin/perl -T --
use strict;
use warnings;
use IPC::System::Simple qw' capturex ';

Main( 'theuser' );
exit( 0 );

sub Main {
    my( $username ) = @_;
#~     my $top = `top -b -n 1 -u $username`;
## Capture text while invoking the shell.
#~     my $top = capturex( qw' top -b -n 1 -u ', $username );
    my $output = <<'__TOP_EXAMPLE__';
here is something top will output
it goes like this
__TOP_EXAMPLE__

    if( $output=~ /.../ ){ # my regex
        print "$1$2...\n";
    }

}