Regex with recursive expression to match nested braces?

Question

I\'m trying to match text like sp { ...{...}... }, where the curly braces are allowed to nest. This is what I have so far:

my $regex = qr/
(             


        

Answer 1

There are numerous problems. The recursive bit should be:

(
   (?: \{ (?-1) \}
   |   [^{}]+
   )*
)

All together:

my $regex = qr/
   sp\s+
   \{
      (
         (?: \{ (?-1) \}
         |   [^{}]++
         )*
      )
   \}
/x;

print "$1\n" if 'sp { { word } }' =~ /($regex)/;