my $braces = qr/(?<braces> { (?: (?: [^{}] | (?&braces) )*+ )* } )/x;

##</code><code>##

my $parens = qr/(\((?:[^()]++|(?-1))*+\))/;
if (/foo $parens \s+ \+ \s+ bar $parens/x) {
   # do something here...
}