Re^2: How do I avoid double substitution when replacing many patterns?

[diotalevi]

The leading $and the middle \w are common between patterns. In fact, all that's required is to require a closing ) only when there was an opening (.

Using a less well known feature

\$ # Our '$' prefix
(?:
    # Optionally *don't* find the opening paren.
  |
    (\() # Optionally find the opening paren
)
(\w+) # The middle part is captured in $2
(?(1)\)) # Require a closing paren only if $1 matched.

Merely removing the prefix

\$ # Our '$' prefix
( # Capture into $1
    (?:
        \w+ # Plain word.
      |
        \( \w+ \) # A word with parentheses around it.
    )
)

[japhy]

You could change

(?:
  |
  ( \( )
)

to

(
  \(
)?

... unless you get queasy when you see quantifiers placed on capturing groups.

[diotalevi]

I thought about it but decided I wasn't sure whether that would work correctly with the later conditional. If it does, great.