Btw, you're using $findfile somewhat incorrectly, $findfile itself is a loop, using it inside your while loop like this makes things much much slower, you could use something like this, which only calls $findfile once ( while your code call $findfile once to get the number of files, and then once each time the loop iterates):

alias FolderSort {
  var %main H:\Anime\
  noop $findfile(%main,*.mkv,0,0, noop $handle_anime(%main,$nopath($1-)))
alias handle_anime {
  var %pattern /(\[HorribleSubs\] .+ -)/iS
  if ($regex($2-,%pattern)) {
    var %f $remove($regml(1),-,[HorribleSubs])
    if (!$isdir($1- $+ %f)) mkdir $qt($1- $+ %f) 
    ; rename $qt($1- $+ $2-) $qt($1- $+ %f $+ \ $+ $2-)

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