Thus my need to know if a key in the table is a literal or a regex so I can do the right test to see if the key matches

Since the regex will have been stringified if used as a hash key, The only way I can think of doing that (if you can't store extra info in the hash value to indicate this) is to see if the key string matches /^\(\?.*\)$/. This will of course fail if an exact string match looks like "(?....)"

Dave.