:port

[syntax] :port vars port

[syntax] :port vars port read-proc

SRFI-42: Reads from the port until the eof-object is read. Providing the default read for read-proc, the generator first evaluates port and read-proc, which must result in an input port p and a procedure r. Then the variable is run through the sequence obtained by (r p) while the result does not satisfy eof-object?.