This one won't explain itself when you run it.

#!/usr/bin/perl
do shift;{($t[$h],$*,$m)=@{$b{$m}{$t[$h]||0}};$h+=$*;$m?redo:die@t,$/}
[download]

If you can't figure out what the input file is supposed to look like, here are some samples:

• <Reveal this spoiler or all spoilers in this node or all in this thread>

• ($m,%b)=(h,j,{0,[h,1]},a,{0,[p,1,j]},p,{0,[a,1,a]},h,{0,[j,1,p]})
  [download]