My point was that only something like "Foo::Bar is my favorite module" should match, not "Foo::Bar()" and " Foo::Bar()" (which changing * to + make match).

As to "missing )", I meant (but put it poorly) in your statement:

Surely trying to match \s* is futile in a negative-lookup? Because \s* can match nothing it will always succeed, thereby never matching??

The assertion wasn't \s*, it was \s*\(, a horse of a completely different color.