Replace a substring in Rw with Rx starting at
Ry for length Rz, and load into Rv. If length is zero, the string Rx is
inserted without replacing any characters.
Parameters:
Rv: A register that will contain
the modified string.
Rw: A register of the string to modify.
Rx | string: A string register
or constant of the substring to copy.
Ry | start: A numeric register
or constant specifying the replace position in Rx.
Rz | length: A numeric register
or constant specifying the number of characters in Rw to replace.