sub f{for($t=pop;$_=(0,l,r)[$$t{d}cmp$_[0]]and$t=$$t{$_};){}$t}

##</code><code>##

sub f{for($t=pop;$_=$$t{d}cmp$_[0]and$t=$$t{$_>0?l:r};){}$t}

##</code><code>##

sub f{for($t=pop;$_=$$t{d}cmp$_[0]and$t=$$t{$_};){}$t}