Something

#!/bin/perl -w

use strict;

my $limit = "95";
my $avail = 'df -h /usr | awk \'/usr/ {print $5}\' | sed s/%//g';

system $avail; #works fine, returns 2

if ( (system $avail) > $limit ) {
        print "There isnt enough Space\n";
        } else {
        print "There is enough Space\n";
}