=< evaluates its head against its tail as subject.

=<(a b) is =>(b a), and =<(a [a=5]) is 5.

irregular forms:

arm:core is =<(arm core)

%: 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)

add sums two atoms.

(add 2 3) is 5.

|% makes a core: a battery of named arms, each written ++ name.

reach an arm back out with =< or arm:core.

=<  a
|%
++  a  5
--

is 5.