butlast --Operation, one input. Abbreviation: bl
     The input may be any non-empty Logo object. If the input is a list,
     the output is a list equal to the input list with the last member
     removed. (If the input list has only one member, the output is the
     empty list, a list of zero members.) If the input is a word, the
     output is a word equal to the input word with the last letter removed.
     (If the input is a single-letter word, the output is the empty word.)
     If the input is empty, an error results.