The command shell is a good way to test an idea or find a quick answer about a function.

In the shell, you can quickly display information about a particular function and its arguments.

In addition the SOURCE function can show you how other functions are written.

>> help func
USAGE:
   FUNC spec body
DESCRIPTION:
    Defines a user function with given spec and body.
    FUNC is a function value.
ARGUMENTS:
    spec -- Help string (opt) followed by arg words (and opt type and string) (Type: block)
    body -- The body block of the function (Type: block)
(SPECIAL ATTRIBUTES)
    catch

>> source func
func: func [
   "Defines a user function with given spec and body."
   [catch]
   spec [block!] {Help string (opt) followed by arg words (and opt type and string)}
   body [block!] "The body block of the function"
][
   throw-on-error [make function! spec body]
]