execute and analyze unix command with perl

[Robert Morales]

Hi,

I want my code to execute the unix free command in order to analyze
the memory state, and issue a warning if the cached memory increases.
I don`t know what I did wrong, but this is what I got for now:

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

# return codes
$ok = 0;
$warning = 1;
$critical = 2;

open(my $memory, "free") or die "Error: $!"; # running unix command "free"

$regex = "^((?!total).)*$";

while (my $line = $vgs){

    if ($line =~ m/$regex/){
        chomp $line;
        my @array = split /\s+/, $line;
        if ($array[6] >= "867580"){
            print "$warning\n";
        }elsif ($array[6] >= "689967"){
            print "$critical\n";
        }else{
            print "$ok\n";
        }
    }
}