I updated my code and have come a little closer to figuring out the issue. When I run this script from the command prompt it returns the expected information, how ever, in Nagios it does not recognize anything sent to it by the array. I tested this by assigning the value of the array to a variable and then sending it to output. The command line prints 4, but nagios prints 0. I am at a loss here Here's the code 
#!/usr/bin/perl

use warnings;
use strict;
use POSIX qw(strftime);
use Date::Calc qw(Delta_Days);

my $domainList = 'domains.txt';
my (@display, $stat, $expDate, $daysLeft, $diff, $spec, $len);
my $date = strftime "%Y-%m-%d", localtime;
my $flag = 0;

open (FILE, $domainList);
my @dom = <FILE>;

foreach my $dm (@dom) {
    chomp $dm;
    $stat = `whois $dm | egrep "Registrar Registration Expiration Date
+|Registry Expiry Date"`;
    $stat =~ m/(\d{4}-\d{2}-\d{2})/;
    $expDate = $1;
    $diff = &dateDiff($expDate);
    $len = length($dm);
    if ($len <= 7) { $spec = $dm."\t\t\t".$diff; }
    if ($len > 7 && $len <=16) { $spec = $dm."\t\t".$diff; }
    if ($len > 16) { $spec = $dm."\t".$diff; }
            
    if ($diff < 28 && $diff > 14) {
        $flag = 1;
    }
    if ($diff <= 14) {
        $flag = 2;
    }
    push @display, "$spec";
}
close FILE;

if ($flag ==  2) {
    my $status = "CRIT: There are Certificates Expiring Soon.  Please 
+Resolve";
    unshift @display, $status;
    print join("\n",@display);
    exit 2;
}

if ($flag == 1) {
    my $status = "WARN: There are Certificates Expiring within a month
+.  Please Resolve";
    unshift @display, $status;
    print join("\n",@display);
    exit 1;
}

else {
    my $status = "OK: Certificates Look good";
    unshift @display, $status;
    print join("\n",@display);
    exit 0;
}

sub dateDiff {
    my $ex = $_[0];

    $ex =~ m/(\d{4})-(\d{2})-(\d{2})/;
    my $y = $1;
    my $m = $2;
    my $d = $3;
    my  @exDate = ($y, $m, $d);

    $date =~ m/(\d{4})-(\d{2})-(\d{2})/;
    my $yLoc = $1;
    my $mLoc = $2;
    my $dLoc = $3;

    my @curDate = ($yLoc, $mLoc, $dLoc);
    my $diffSub = Delta_Days(@curDate, @exDate);

    return($diffSub);
}

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In reply to Nagios custom Perl check by edimusrex

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