The other day I was playing with HTML::TableExtract that uses a very similar mechanism to scan for table column headers. It failed very oddly when a parenthesis or | was in the header name.

For what it's worth, I do mention in the TE docs that header strings get turned into case-insensitive regular expression strings...so regexp special characters need to be escaped first.

Perhaps more insidious, however, is when people are dealing with headers that have one as a substring of another. Order is important in that case. Think m/Hubba|Hubbadandy/ and you'll see what I mean. It's not hard to fix, but I need to patch to issue a warning since ordering of columns is a feature of the module.

Matt