The Pipe interface establishes a pipe as a PSL channel from which (or to which) normal PSL
read/write operations can be used. Pipes are specially useful to supply data to other processes,
e.g. REDUCE uses it to send data to a plot program.
(pipe!-open S:string M:Mode): integer expr
Pipes are closed with a normal close call. This will kill the process that has been started. If this
process should survive, you have to use abandonpipe.
(abandonpipe channel): void expr