You can call them without `()`, when it's clear otherwise, that it's a call.
Say, in command syntax with arguments: `a b` (means `a(b)`). In dot syntax:
`b.a`.
In just `a` on its own `a` represents just the proc itself, so that you can
send it as an argument to other procs or save to a variable, like: `mySeq.map
toUpperAscii`, `toUpperAscii` is not called here, but passed to `map`. Or:
proc x(s: string) = echo "[", s, "]"
var y = x
y "z"
Run
And as just `quit` returns the proc itself, it is an expression ('None' is its
type), not a statement.
