g1smd - 11:12 pm on Jan 24, 2012 (gmt 0)
If your pattern is start-anchored then it will match only a single character before the first slash. Your example showed two characters.
If there is no start anchoring it will match any number of characters before the first slash, but only if the last one before the slash is an upper case letter.
If there is no end anchoring it will match any number of characters after the final slash and two digits have been matched.