Currently "ant test" performs several saniy cheks on regular expressions (POS tags or token strings) in rules/*/grammar.xml which helped catching several issues.
Those tests are currently not run on regexps in resources/*/disambiguation.xml.
It would be nice to run them for disambiguation.xml too.
The syntax of pattens/token/exception/regexp is pretty much the same as in grammar/*rules.xml so it should be possible.
I suspect that it would find several issues there, especially since some language are having large disambiguation.xml files now.