#!/usr/bin/perl --

use strict;
use warnings;

Main( @ARGV ? @ARGV : qw' 123 555 7672676' );
exit(0);

sub Main {
    for my $num (@_) {
        my @n = MakeN($num);
        for my $n (@n) {
            print "permute: $n\n";
            print join( "", @$_ ), "\n" for permute( NumberList($n) );
        }
        print "\n";
    } ## end for my $num (@_)
} ## end sub Main

sub MakeN {
    my $n = join '', @_;
    my @n;
    while ( 3 <= length $n ) {
        push @n, $n;
        chop $n;
    }
    @n = reverse @n;
    @n;
} ## end sub MakeN

sub NumberList {
    my %lettermap = (
        1   => [' '],
        2   => [qw' a b c '],
        3   => [qw' d e f '],
        4   => [qw' g h i '],
        5   => [qw' j k l '],
        6   => [qw' m n o '],
        7   => [qw' p q r s '],
        8   => [qw' t u v '],
        9   => [qw' w x y z '],
        0   => [' '],
        '*' => [qw' + '],
        '#' => ['#'],
    );
    return @lettermap{ split //, join '', @_ };
} ## end sub NumberList

## http://perlmonks.org/?node_id=24270# Permutations and combinations
sub permute {
    my $last = pop @_;
    unless (@_) {
        return map [$_], @$last;
    }
    return map { my $left = $_; map [ @$left, $_ ], @$last } permute(@_);
} ## end sub permute

__END__