- send/blocking! PIGEON-HOLE VALUE #!optional BLOCKprocedure
Send VALUE to PIGEON-HOLE, blocks if capacity is reached.
BLOCK is either a boolean or a procedure taking the queue as argument and returning a boolean. If it is a procedure it is call in tail position when the call would block. If #f does not block but return #f. Default if #t: block for capacity.
Return: #t if value was send.