my %hash;
for my $element (@array) {
    my ($prefix, $first, $second) =
        $element =~ /^([A-Z])(\d+):(\d+)$/;
    my @matches = ( $prefix . '0:' . $second - 1,
                    $prefix . $first * 2 . ':' . $second - 1);
    $hsh{$element} = [ grep {
            $_ eq $matches[0] or $_ eq $matches[1]
        } @array ];
}