> and I need to find the first occurrence of "+" that is not enclosed within parenthesis, i.e. the one before "5", how would I do that with a regular expression ?

depends what you mean with "finding"!

If it's just the position you need, a simple technique I like is to replace all inner paren-pairs till you get a "cleaned" string and then to try finding whatever it needs.

This demonstrates the intermediate results: 

  DB<172> $s=$s0
 => "1*((2+3)*((3+4)+5))*(6+7)+8"

  DB<173> print "$s\n" while $s =~ s# \( [^()]* \) # '.' x length($&) 
+#gex 
1*(.....*(.....+5))*.....+8
1*(.....*.........)*.....+8
1*.................*.....+8

  DB<174> index $s, '+'
 => 25

[download]

Cheers Rolf

( addicted to the Perl Programming Language)

In reply to Re: Regex: first match that is not enclosed in parenthesis by LanX
in thread Regex: first match that is not enclosed in parenthesis by monkprentice

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