As koolade pointed out, not all of these work. Yours in particular goes into deep recursion. Works in theory is not good enough, in golf you are going to learn a lot about the assumptions you cannot make. And yours has at least 2 separate (and serious) mistakes.

BTW the counts as I list them are just for the body of the sub, so if yours did work it would be 51 characters.

Playing independently I came in with several solutions that are small, and the following which is similar to yours really does work at 58: 

sub f {
my($s,$t)=@_;$t?$$t{d}eq$s?$t:f($s,$$t{l})||f($s,$$t{r}):0
}

[download]
And here, thanks to koolade, is the test that I use: 
$t = {
    d => 'd',
    l => {
        d => 'b',
        l => { d => 'a', l => 0, r => 0, },
        r => { d => 'c', l => 0, r => 0, },
    },
    r => {
        d => 'f',
        l => { d => 'e', l => 0, r => 0, },
        r => { d => 'g', l => 0, r => 0, },
    }
};

sub test {
  my $val = f(@_);
  print $val ? "$val->{d}:$val\n" : "$val\n";
}

test('e',$t);
test('O',$t);

[download]

In reply to Re (tilly) 3: Golf: Tree searching by tilly
in thread Golf: Tree searching by Masem

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