I'd say look at prior art, but "end" in this role isn't very common. It
shows up in AppleScript, where it does double duty: "end" serves as an index
in ranges ("items 3 through end of someList"), but by itself it returns the
last item, not the last index ("end of someList"), and as a lone index it
doesn't work ("item end of someList" is an error).
Most languages that have a named function or method for this sort of access
seem to use a form of "last" instead. And it's almost always the value, not
the index. Maybe P6 could have both .last and .end, where one is the item
and one is the index? But while my intuitive expectation is that "last" is
the item and "end" is the index, it's not very a strong intuition, and I
could easily see someone having the opposite expectation.
One argument for making "end" the index is that the last value is more
easily obtained via other means, but it's really not hard to go either way.
If $list.end is the last index, then $list[$list.end] gets you the last
value, although that would usually be written $list[*-1]. And if $list.end
is the last value, then $list.keys.end is the last index...
