#;2> (use r7rs)
#;3> bytevector-copy!

Error: unbound variable: bytevector-copy!
#;3> (import scheme.base)

Note: re-importing already imported syntax: cond-expand

Note: re-importing already imported syntax: define-record-type

Note: re-importing already imported syntax: include
#;4> bytevector-copy!
#<procedure (r6rs.bytevectors#r6rs:bytevector-copy! source491 source-start492 target493 target-start494 count495)>
#;5>