#!/usr/bin/perl
use warnings;
use strict;

my $mode = fetch('Enter mode', 1);

while (my $raw_wwn = fetch($mode eq 'a' ? "wwn (no ':')" : "wwn with ':'")) {
    if ($mode eq 'a') {
        if ($raw_wwn =~ /[^0-9a-fA-F]{16}$/) {
            print "Invalid Length Or Incorrect Format\n";
        } else {
            print join (":", unpack ("(a2)*", lc ($raw_wwn))), "\n";
        }

        next;
    }

    if ($raw_wwn =~ /[^:a-fA-F0-9]{23}$/) {
        print "Invalid Length Or Incorrect Format\n";
        next;
    }

    $raw_wwn =~ s/://g;
    print "$raw_wwn\n";
}


sub fetch {
    my ($prompt, $key) = @_;

    $prompt .= ' or q to quit' if $prompt;

    while (1) {
        print <<KEY if $key;
Enter
   a for lowercase and colons.
   b to do it the other way around.
   q to quit
KEY
        print "$prompt: " if $prompt;

        my $answer = lc <>;

        chomp $answer;
        exit if $answer eq 'q';
        return $answer if $key && $answer =~ /^[ab]$/;
        return $answer if ! $key;

        print qq{"$answer" is not a valid mode.\n\n};
    }
}