[tex-live] TeX Live 2010 : odd behaviour after moving to spare system on removable disc

[Philip TAYLOR]

Philip TAYLOR wrote:

> Now, SELFAUTOLOC makes some vague sort of sense : "this is
> the automatically determined location of myself", where
> "myself" is some arbitrary TeX binary; but "SELFAUTOPARENT"
> to refer to the /grand/parent directory just blows my mind.
> I am sure that Karl had a good reason to choose these names,
> but they are not exactly self-explanatory, by any stretch
> of the imagination !

(Heiko's explanation of "OPA" much appreciated but may not
help me to remember the semantics ... !).

So now, a new question.  What do SELFAUTODIR and SELFAUTOPARENT
add ?  Why can I not replace the former by $SELFAUTOLOC\.. and
the latter by $SELFAUTOLOC\..\.. ?  Why are the latter two needed
at all ?

** Phil.