use Benchmark 'cmpthese';
cmpthese(-3, {
   plain => sub { my $x; ($x) = /^([01])[01]*$/ foreach qw(0 1 00 11 10 01 000x00) },
   capture_in_lookahead => sub { my $x; ($x) = /^(?=(.))[01]+$/ foreach qw(0 1 00 11 10 01 000x00) },
   lookahead_then_capture => sub { my $x; ($x) = /^(?=[01]+$)(.)/ foreach qw(0 1 00 11 10 01 000x00) },
});