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

print <<HEREDOC;
Enter:
    a for lowercase and colons.
    b to do it the other way around.
    q to quit
HEREDOC

while (my $choice = lc <>) {
    chomp $choice;
    
    last if $choice eq 'q';
    
    if ($choice !~ /^[ab]$/) {
        print "a, b or q expected: ";
        next;
    }

    my $wwn = lc <>;
    
    if ($choice eq 'b') {
        $wwn =~ s/://g;
        print "$wwn\n";
        next;
    }
    
    if (-1 < index $wwn, ':') {
        print "WWN already contains :\n";
        next;
    }

    if (16 != length $wwn) {
        print "WWN must be 16 characters\n";
        next;
    }

    if ($wwn =~ /^[a-f0-9]/) {
        print "Non-hex characters are not allowed in WWN\n";
        next
    }

    print join (':', unpack ("(a2)*", $wwn)), "\n";
}