I can shorten it to 43.

sub f {
($a=shift)=~s/_/[^$a]/g;grep/^$a$/i,@{+pop}
#23456789_123456789_123456789_123456789_123
}
[download]

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;