If the input is a word, BUTLAST outputs a word containing all but the last character of the input. If the input is a list, BUTLAST outputs a list containing all but the last member of the input.
BUTLAST throws a bad input error if given the empty list, the empty string, or an array.
SHOW BUTLAST [1 2 3][1 2]
SHOW BUTLAST "HelloHell