(?<=.+).+(?=</a>)
Most regex engines do not support regex pattern matching inside a
lookbehind. According
regular-expressions.info<http://www.regular-expressions.info/lookaround.html>,
the only engines that do are provided by JGsoft, and the .NET framework.
I believe TextMate uses the Oniguruma regex engine.
See if this one meets your needs instead:
(?<=>).*(?=\<\/a\>)