( 10-most-frequent-words
  =     MergeSort                        { Local variable declarations. }
        types
        sorted-words
        frequency
        type
        most-frequent-words
    .   ( MergeSort                      { Definition of function MergeSort. }
        =   A N Z pivot
          .   !arg:? [?N                 { [?N is a subpattern that counts the number of preceding elements }
            & (   !N:>1                           { if N at least 2 ... }
                & div$(!N.2):?pivot               {     divide N by 2 ... }
                & !('($arg:?A [($pivot) ?Z))      {     split list in two halves A and Z ... }
                & MergeSort$!A+MergeSort$!Z       {     sort each of A and Z and return sum }
              | !arg                              { else just return a single element}
              )
        )
      &     MergeSort             { Sort }
          $ ( vap                 { Split second argument at each occurrence of third character and apply first argument to each chunk. }
            $ ( (=.low$!arg)      { Return input, lowercased. }
              .   str
                $ ( vap           { Vaporize second argument in UTF-8 or Latin-1 characters and apply first argument to each of them. }
                  $ ( (
                      =
                        .   upp$!arg:low$!arg&\n  { Return newline instead of non-alphabetic character. }
                          | !arg                  { Return (Euro-centric) alphabetic character.}
                      )
                    . get$(!arg,NEW STR) { Read input text as a single string. }
                    )
                  )
              . \n                       { Split at newlines }
              )
            )
        : ?sorted-words                  { Assign sum of (frequency*lowercasedword) terms to sorted-words. }
      & :?types                          { Initialize types as an empty list. }
      &   whl                            { Loop until right hand side fails. }
        ' ( !sorted-words:#?frequency*%@?type+?sorted-words    { Extract first frequency*type term from sum. }
          & (!frequency.!type) !types:?types                   { Prepend (frequency.type) pair to types list}
          )
      &   MergeSort$!types                                     { Sort the list of (frequency.type) pairs. }
        : (?+[-11+?most-frequent-words|?most-frequent-words)   { Pick the last 10 terms from the sum returned by MergeSort. }
      & !most-frequent-words                                   { Return the last 10 terms. }
  )
& out$(10-most-frequent-words$"135-0.txt")      { Call 10-most-frequent-words with name of inout file and print result to screen. }