snippet
BooK
<p>This subroutines count the number of capturing parentheses in a compiled regular expression. Since the regexp is compiled, we know it's correct, and thus we only have to count the opening parentheses.</p>
<p><b>Update:</b> added <tt>/s</tt> in the while condition.</p>
<p><b>Update:</b> [id://349891|This other discussion] led to
a much better solution, so I commented out the original code.</p>
<CODE>
#sub captures {
# local $_ = shift;
# croak "$_ is not a compiled regexp" unless ref eq 'Regexp';
# my $n = 0;
# while( /\G(?=.)/gcs ) {
# /\G[^\\(]*/gc; # ignore uninteresting stuff
# /\G(?:\\.)*/gc; # ignore backslashed stuff
# /\G\(\?/gc; # ignore special regexps
# /\G\(/gc && $n++; # a capturing (, count it!
# }
# $n;
#}
sub captures { ( @_ = '' =~ /(@{[shift]})??/ ) - 1; }
</CODE>