The ->BIN function converts the byte array or the string on top of the stack to its binary representation.
Since the 2.8.0 version, it also converts a LONG to its 64 bits binary representation. Thus, this function and TOBIN are equivalent.
Applied on a string,
'utf-8' ->BYTES ->BIN
If the encoded content is not a valid UTF-8 representation, the resulting string will reflect that.