I’m starting to use shortcodes heavily in WordPress1 as we are using it internally on the DEPtH project to coordinate our new TouchIT book. There was minor bug which meant that HTML tags came out unbalanced (e.g. “<p></div></p”).
I’ve just been fixing it and posting a patch2, interestingly the bug was partly due to the fact that back-references in regular expressions count from the beginning of the regular expression, making it impossible to use them if the expression may be ‘glued’ into a larger one … lack of referential transparency!
For anyone having similar problems, full details and patch below (all WP and PHP techie stuff).