Alan,
The OED says:
prepend, v.1 rare.
trans. To weigh up mentally, ponder, consider; to premeditate. Also intr.
Although the sense of premeditation is sometimes apparent, in many instances the apparent suggestion of a more general sense of consideration suggests mistaken use for PERPEND v.
(Which makes me wonder whether Chi accepts "perpend"?)
AND
prepend, v.2 Chiefly Computing.
trans. To add at the beginning, to prefix, prepose; esp. to add or append (a character, string, file, etc.) at the front of an existing string, file, etc.
With a usage example from 2000! to wit: "2000 Proc. National Acad. Sci. U.S.A. 97 1755/2 To further reduce motion artifact, a 32-point navigator echo was prepended to each phase-encode echo."
Thanks,
Ellen Fremedon