This seems like a good place to mention that you'll need to place use statements in a startup block to take advantage of any Perl 5.10-isms.
Code slightly modified from an example in Advanced Perl 2nd Edition:
use Modern::Perl;
use Parse::RecDescent;
my $grammar = q{
{ use Modern::Perl }
GameTree : "(" Sequence GameTree(s?) ")"
Sequence : Node(s)
Node : ":" Property(s) { say "I saw a node!" }
Property : PropIdent PropValue(s)
PropIdent : /[A-Z]+/
PropValue : { extract_bracketed($text, '[ ]') }
};
my $sgf_parser = Parse::RecDescent->new($grammar);
undef $/;
my $sgf = <DATA>;
say $sgf_parser->GameTree($sgf);
__DATA__
(:GM[1]FF[4]AP[CGoban:2]ST[2]RU[Japanese]
PW[Honinbo Shuwa]PB[Yasuda Shusaku]
WR[7d]BR[5d]
:B[qd]:W[dc]:B[pq]:W[oc]:B[cp]:W[qo]
:B[pe]C[This is the famous Shusaku opening".])
I could be wrong, of course. This is how I got the thing to run with say in the action, though.