perl -MIO::Socket::INET -le "do{$s=IO::Socket::INET->new(PeerAddr=>'12
+7.0.0.1',PeerPort=>$_,Timeout=>1);print $s? $_.' OPEN' : $_.' CLOSED'
+}for ARGV[0]..$ARGV[1]" 1 1024
[download]

You should also check out the Perl Power Tools Project which has ported many of the popular *nix command line tools to Perl.

The nmap utility may already do what you want, unless you're interested in re-writing this utility from scratch, in Perl, as a learning exercise.

I want to do it to learn from, I don't want to use real system commands that are there. I want to do it via Perl.

Nmap can be found at www.insecure.org/nmap.

pscanner.pl

Teabag

#!/usr/bin/perl
use warnings;
use IO::Socket;

# scan($port, $end_port, $target); 

scan(1, 2500, '192.168.0.1');

  sub scan {
    my ($from, $to, $where) = @_;
    print "Scanning $where | from port $from to $to\n\n";
    for my $p ($from .. $to) {
      print "Port $p is open\n" if IO::Socket::INET->new(
        PeerAddr => $where,
        PeerPort => $p,
        Proto => 'tcp',
        Timeout => 1,
      );
    }
    print "Port scan complete\n\n";
}
[download]