I don't quite understand what you're trying to do, but I'll try to help in spite of that. ;-)

It sounds like you may not need to use regular expressions at all, just simple string equality. If parts of the input string are fixed (like the colon delimiters), and you need to see if a piece changes, you can split the input line, and just do a string compare (using eq, that is).

Unless I've completely misunderstood what you're trying to do, which is quite possible....