thanks! you pointed me in the right direction. i ended up with this code:

#!/usr/bin/perl
#
# App Name:    pscan.pl
# Written By:     DKD (dale_d at telusplanet dot net)
# 
# uses nmap, fuser, and ps to display the port number,
# protocol, pid, and executable name for each open
# port in a readable format.
#
# Requires:    nmap, fuser, ps 
#
# Usage:     pscan.pl
#        No switches

use strict;

# Variables

my @temp;
my @nmap;
my @port;
my @protocol;
my @pid;
my @pids;
my @app;
my $whoami;
my $junk;
my $i;

# Check to see if you are root, and then display some text.

$whoami = `whoami`;
chomp($whoami);
die "You must run pscan as root!\n" unless ( $whoami eq "root");
print "\nScanning for open ports.";

# Grab input from nmap and discard any output lines that we
# don't want (any that don't start with numeric characters).

chomp(@temp = `nmap localhost`);
foreach (@temp) {
    push(@nmap, $_) if $_ =~ /^\d+/;
}

# Iterate through the output from nmap and extract the port
# and protocol, then use the port and protocol to get the
# PID from the fuser command, then use ps to get the name of
# the executable from the pid.

$i = 0;
foreach (@nmap) {
    (@port[$i], @protocol[$i]) = split /\//, $_;
        @protocol[$i] = split / /, @protocol[$i];
        @pid[$i] = `fuser -n @protocol[$i] @port[$i]`;
        chomp(($junk, @pid[$i]) = split /:\s+/,@pid[$i]);
    chomp(@app[$i] = `/bin/ps --no-headers -o %c @pid[$i]`);
        $i++;
    print ".";
}

# Display the data in a readable format

print "done." . "\n" x 2;
# print the header
print "  The following ports are open on your system:\n\n";
printf "%8s%12s%12s%16s\n","Port", "Protocol", "PIDs", "Process";
print "-" x 48 . "\n";
$i = 0;
foreach (@nmap) { # print the port, protocol, first pid, and app(proc)
    chomp(@pids = split / +/, @pid[$i]);
    printf "%8s%12s%12s%16s\n", @port[$i], @protocol[$i], shift(@pids)
+, @app[$i];
    foreach (@pids) { # print any pids if there are more than one.
        printf "%32s\n", $_;
    }
    print " -" x 24 ."\n"; # dashed line separating each port
   ++$i;
}
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