muggle.rb

@_,$_,@__=->_,__{_==''?_:(__[_[$_-$_]]?_[$_-$_]:'')+@_[_[$_..-$_],__]},$$/$$,->_{__,___=_[$_-$_],_[$_..-$_];_==''?_:@__[@_[___,->_{_<__}]]+__+@__[@_[___,->_{_>=__}]]};($__=->*_{__=@__[_[$.]];$*[$_-$_]==__ ?_:$*<<__;_[$.+=$_]?$__[*_]:!$*[$_]})['allergy', 'gallery', 'largely', 'regally']

# The opening variables were defined in parallel to increase confusion, so let's undo that.

$_ = $$ /$$ # 1, because we'll need -1, 0, and 1.

# @_ = ->_,__{_==''?_:(__[_[$_-$_]]?_[$_-$_]:'')+@_[_[$_..-$_],__]}
# @_ is a string filter:

# @_ = ->_,__{
filter = -> str, pred {
  # _==''?_:
  str == '' ? str :              # If empty, nothing to filter; return. Otherwise,
  # (__[_[$_-$_]]?_[$_-$_]:'')+
  (pred[str[0]] ? str[0] : '') + # keep the head only if it satisfies the predicate
  # @_[_[$_..-$_],__]}
  filter[str[1..-1], pred]       # and add it to the filter applied to the tail.
}

# @__=->_{__,___=_[$_-$_],_[$_..-$_];_==''?_:@__[@_[___,->_{_<__}]]+__+@__[@_[___,->_{_>=__}]]}
# @__ is ex-situ Quicksort:

# @__=->_{
sort = -> str {
  # __,___=_[$_-$_],_[$_..-$_];
  pivot, rest = str[0], str[1..-1] # Head used as pivot for simplicity.
  # _==''?_:
  str == '' ? str : # If empty, nothing to sort; return. Otherwise,
  # @__[@_[___,->_{_<__}]]+
  sort[filter[rest, -> chr {chr <  pivot}]] + # Concatenate the sorted lesser characters
  # __+
  pivot +                                     # with the pivot
  # @__[@_[___,->_{_>=__}]]}
  sort[filter[rest, -> chr {chr >= pivot}]]   # and the sorted greater-or-equal characters.
}

uniqs = $* # ARGV, used as an initially empty pseudo-set.
index = $. # ARGF.lineno, 0 at program start.

# $__=->*_{__=@__[_[$.]];$*[$_-$_]==__ ?_:$*<<__;_[$.+=$_]?$__[*_]:!$*[$_]}
# $__ is all_anagrams:

# $__=->*_{
all_anagrams = -> *words {
  # __=@__[_[$.]];
  sorted = sort[words[index]]
  # $*[$_-$_]==__ ?_:$*<<__;
  uniqs[0] == sorted ? 0 : uniqs << sorted # Add the sorted word if it's new.
  # _[$.+=$_]?
  words[index += 1] ?     # If there is another word to consume,
  # $__[*_]:
  all_anagrams[*words] :  # go again with the increased index. Otherwise,
  # !$*[$_]}
  !uniqs[1]               # the arguments were anagrams if uniqs is of length 1.
}