Comment by uryga

> But at the same time this seems to require colons after... what exactly?

not 100% sure but it kind of looks like copper's Whole Deal™ are "object-functions" (closures?) and you use colons to get an object function's return value. something like this

  adder = [a b]{ ret(this.a + this.b) }
  x = adder(3 5)
  print(x.a x.b x:) # 3 5 8

(i looked at the docs for like 10 minutes, could be wrong)