my $C='((w)hite|(b)lack)';

my @c;
my @d;
while (<DATA>) {
    if (/$C\s+"princepawn"/i) {
        push @c, [ // ];
        push @d, [ $1, $2 || $3 ];
    }
}

use Data::Dumper;
print Dumper(\@c); # What you said
print Dumper(\@d); # ['black', 'b'] or ['white', 'w']
__DATA__
white "princepawn"
foo
black "princepawn"