Regular expression in conditional build rule?

[Rogier]

You can put conditional rules on build steps by selecting 'Build only if macro or expression...' and then there's options like 'is true', 'contains (x)', 'is not equal to (y)' etc.

It would be really great if you could add 'matches regexp (x)' and 'does not match regexp (y)' there!

Or is there some other way to pull this off?