in reply to Alternation in Effective Perl Programming Example
It's a little more than that. Should it be (?:\\\W|.) instead?
If so, as written, it would be interpreted as non-capturing parenthesis, matching either a backslash and a nonword character or a single character.
Otherwise, it's (an optional colon followed by a backslash and a non-word character) or (a single character).
In Section Seekers of Perl Wisdom