sub f{
#2345678901234567890123456789012345678901
(my$i=shift)=~y/_/./;grep/^$i$/i,@{$_[0]}
}

##</code><code>##

sub f{
#234567890123456789012345678901234567890123456789012345
my$a=shift;(my$b=$a)=~s/_/[^$a]/gi;grep/^$b$/i,@{$_[0]}
}