I'm confused by your post. Breaking down qr/Foo::Bar(?!\s+\()/ we get:
  Foo::Bar  # literal 'Foo::Bar'
  (?!       # start of negative look-ahead
    \s+     # one or more white space chars
    \(      # literal opening bracket
  )         # end of negative look-ahead

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so to answer your reply, I believe I provided the literal ( after the \s*.

To answer your other statement, that something such as "Foo::Bar is my favourite module" should match, I agree - that is how I read the initial requirement from the thread. In which case my answer of using \s+ kept within the spirit of the original statements made by the thread author. However I wanted to keep my example in line with the example that the author had tried, hence the use of the literal (. Hope this clears up my answer.

In reply to Re^3: Negative Lookahead Assertion Problem by monarch
in thread Negative Lookahead Assertion Problem by Limbic~Region

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