http://qs1969.pair.com?node_id=251185


in reply to How do I replace certain character if condition exists

Possibly a simplistic solution, but have you tried using negative lookahead? For instance: 
abowley@krait:~$ (echo 'Madrid(Spain' && echo 'Madrid(Spain)') | perl 
+-pe 's/\((?![^)]*\))/ /g;'
Madrid Spain
Madrid(Spain)

[download]
Breaking the regex down: 
s/
  \(      # an open bracket
  (?!     # _not_ followed by
    [^)]* # anything except brackets (e.g. 'Spain')
    \)    # followed by a bracket
  )
 / /gz;

[download]

Replies are listed 'Best First'.
Re: Re: How do I replace certain character if condition exists
by Bilbo (Pilgrim) on Apr 17, 2003 at 13:41 UTC

    This works if you are sure that you won't have any nested parentheses. If you do then it doesn't work at all, for example: 

    a(b(c))           becomes a b(c))
a (b (c) d (e) f) becomes a  b (c) d (e) f)
[reply]
      Well, you can do that with a regex, but it's a good degree more complicated..... 
      abowley@krait:~$ (echo 'Madrid(Spain(Europe)' && echo 'Madrid(Spain(Eu
+rope))' && echo 'Madrid(Spain Europe))' && echo 'a(b(c))' && echo 'a 
+(b (c) d (e) f)') | perl -mstrict -wpe 'BEGIN { $brackets = qr#\([^()
+]*(?:(??{$brackets})[^()]*)*\)# }; s#([^)]+?)($brackets)([^(]+)# ( my
+ $s = $1 ) =~ tr/(/ /; ( my $e = $3 ) =~ tr/)/ /; $s . $2 . $e #ge;'
Madrid Spain(Europe)
Madrid(Spain(Europe))
Madrid(Spain Europe) 
a(b(c))
a (b (c) d (e) f)

      [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom