The Number::Format module would work for this:

    #!/usr/bin/perl -w

    use strict;
    use Number::Format qw(:subs :vars);

    $NEG_FORMAT = "x";

    print format_picture(123456789012345, 'No-###-#####-#######');

    __END__
    Prints:

    No-123-45678-9012345
[download]

Note: the above code generates a warning in the module but that is probably easily fixed.

--
John.