Erm, you pretty much answered your own question (although I'm not quite sure where you cooked up the system("telnet $_") from). 
open HOSTS, '<', 'hostnames.txt' or die "Cant open hostnames.txt\n";

while (my $host = <HOSTS>) {
    chomp($host);
    check_ports($host,$timeout,\%porthash);
    # Do other processing stuff here
}

[download]

Cheers,
Darren :)

I strongly suspect that you are going to ask next how to use IO::Socket::PortState, given that you appear to have simply copy/pasted the example code from the documentation - but I may be wrong :)

Update: Okay, since somebody suggested that my initial response to your question may have been a bit mean (and because deep down I really am a very nice guy™), here is some tested and working code that gives the output you are looking for: 

#!/usr/bin/perl -w
use strict;
use IO::Socket::PortState qw(check_ports);

my $hostfile = 'hosts.txt';

my %port_hash = (
        tcp => {
            22      => {},
            443     => {},
            80      => {},
            53      => {},
            30032   => {},
            13720   => {},
            13782   => {},
            }
        );

my $timeout = 5;

open HOSTS, '<', $hostfile or die "Cannot open $hostfile:$!\n";

while (my $host = <HOSTS>) {
    chomp($host);
    my $host_hr = check_ports($host,$timeout,\%port_hash);
    print "Host - $host\n";
    for my $port (sort {$a <=> $b} keys %{$host_hr->{tcp}}) {
        my $yesno = $host_hr->{tcp}{$port}{open} ? "yes" : "no";
        print "$port - $yesno\n";
    }
    print "\n";
}

close HOSTS;

[download]

The above gives the following output: 

Host - 1.2.3.4
22 - no
53 - no
80 - yes
443 - yes
13720 - no
13782 - no
30032 - no

Host - 5.6.7.8
22 - yes
53 - no
80 - yes
443 - yes
13720 - no
13782 - no
30032 - no

[download]

Note that I changed a few of the port numbers to those that I knew would be open on the hosts I tested against, and (obviously) altered the ouput to protect the innocent :)

In reply to Re: Testing for port connectivity by McDarren
in thread Testing for port connectivity by Anonymous Monk

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