We were just talking about this in the CB this morning. You beat me to it, Muskrat (:

Here's an Audio::Beep version I was working out. I think I have the math worked out, but it's kinda hard since I'm not sure of the sample rate of a PC speaker.

#!/usr/local/bin/perl
use strict;
use warnings;
use Audio::Beep;

# Generate DTMF tones
# 

use constant SAMPLE_RATE => 8000;
use constant PI          => 3.14159;
use constant DURATION    => 500;
my %tones = (
    1  => [ 1209, 697 ], 
    2  => [ 1336, 697 ], 
    3  => [ 1477, 697 ], 
    a  => [ 1633, 697 ], 

    4  => [ 1209, 770 ], 
    5  => [ 1336, 770 ], 
    6  => [ 1477, 770 ], 
    b  => [ 1633, 770 ], 

    7  => [ 1209, 852 ], 
    8  => [ 1336, 852 ], 
    9  => [ 1477, 852 ], 
    c  => [ 1633, 852 ], 

    *  => [ 1209, 697 ], 
    0  => [ 1336, 697 ], 
    '#'=> [ 1477, 697 ], 
    d  => [ 1633, 697 ], 
);

my $number = pop;
$number =~ s/[-\(\)]//g;
my $i = 1;

foreach (split //, $number) {
    my $time = $i / SAMPLE_RATE;
    my ($f1, $f2) = @{ $tones{$_} };
    my $freq = 63 * sin($time * 2 * PI * $f1);
    $freq   += 63 * sin($time * 2 * PI * $f2);
    $freq   += 128;

    print "$_: $freq\n";
    beep($freq, DURATION);

    $i++;
}
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----
Reinvent a rounder wheel.

Note: All code is untested, unless otherwise stated