From the holy book of the camel:

splice ARRAY, OFFSET, LENGTH, LIST
splice ARRAY, OFFSET, LENGTH
splice ARRAY, OFFSET
This function removes the elements designated by OFFSET and
LENGTH from an array, and replaces them with the elements
of LIST, if any. The function returns the elements removed
from the array. The array grows or shrinks as necessary. If
LENGTH is omitted, the function removes everything from
OFFSET onward.

I'm not sure (not too familiar with splice) if you could set a length of 0, and do:

splice @a, 2, 0, 'foo'

Any takers care to deny or confirm this?

-marius

Update:redcloud, and a few others have either posted or CB'd me to let me know it works. woohoo! =]