|^ runs its first line against a battery of helper arms written below it - like |-, but with named helpers instead of a self-call.

|^  (double 4)
++  double
  |=  n=@
  (mul 2 n)
--

is 8.

%: calls a gate with several arguments, gathering them into one sample.

%:(add 2 3) is 5.

irregular forms:

(gate a b c) is %:(gate a b c)

|= makes a gate: a function with one named sample, then a body.

the body runs with the sample bound.

call the gate to run it.

(|=(a=@ (add a 1)) 4) is 5.

$= wraps a mold with a face, naming the value it produces.

$=(x @) is the mold x=@.

add sums two atoms.

(add 2 3) is 5.