use strict;

sub find_inB {
    my ($data_hr, $string) = @_;
    my $no_result = 'no result';
    return (
        exists $$data_hr{ $string }
            ? $$data_hr{ $string }
            : exists $$data_hr{ lc $string }
                ? $$data_hr{ lc $string }
                : $no_result
    );
}

sub look_for_dataB {
    my %hash = map { ($_, 'xxx'); } qw( A B C D );
    print "D: " . find_inB(\%hash , 'D') . "\n";
    print "A: " . find_inB(\%hash , 'A') . "\n";
    print "B: " . find_inB(\%hash , 'B') . "\n";
    print "B: " . find_inB(\%hash , 'B') . "\n";
}

print "# look_for_dataB:\n";
look_for_dataB();

__END__
# look_for_dataB:
D: xxx
A: xxx
B: xxx
B: xxx