#!/usr/bin/perl
use strict;
use warnings;

open(STAT, '-|', 'vmstat 2') or die "Could not open pipe: $!";

my $count; # not necessary, just for demonstration

while (<STAT>){
        last if $count++ > 5; # we don't want more than 5 lines of output
        print $_, "\n";
}

print "...done\n";