unless (    ( $display =~ /^[\w-]+$/ ) # Can contain chars, digits, _ 
+and -
         && ( $display !~ /^\d+$/    ) # But not just digits
       )
{
    # String failed to validate.
}
[download]

If you're having trouble with the regexps presented, I suggest you give perlre a good long read -- they only get worse from here. :-)

Those who know that they are profound strive for clarity. Those who
would like to seem profound to the crowd strive for obscurity.
            --Friedrich Nietzsche