sub decipher {
@n=split//,'_abcdefghijklmnopqrstuvwxyz.';$l{$n[$_]}=$_ for 0..$#n;@c=map{$l{$_}}split//,pop;$p[$_[0]*$_%@c]=$n[($c[$_]+$_)%@n]for 0..$#c;join'',@p
}

##</code><code>##

@n=(_,a..z,'.');map{$l{$n[$_]}=$_}0..27;@c=map{$l{$_}}split//,pop;$p[$_[0]*$_%@c]=$n[($c[$_]+$_)%@n]for 0..$#c;join'',@p