use strict;
use warnings;
my $qablock = [
    [qw(r0c0 r0c1 r0c2)],
    [qw(r1c0 r1c1 r1c2)],
    [qw(r2c0 r2c1 r2c2)],
];
my $answer = 'r1c0';
my ($usefulans) = grep {$$_[0] eq $answer} @$qablock;
print "\t\t----> @$usefulans\n";