"i can understand valid selectors:"

"Unary:"
#yourself numArgs = 0.

"Binary:"
#'**' numArgs = 1.

"Keywords"
#at: numArgs = 1.
#at:put: numArgs = 2.


"But does anyone knows what the following cases are meaning?"
#'a:b:c' numArgs = 1.
#'a::bc' numArgs = 1.
#':abc:' numArgs = 0.
#'::abc' numArgs = -1.
#':abc' numArgs = -2.


#':::' numArgs. "make your guess here"


"Nicolas"