arrays and insert/select

I'm loading a table from another (in 7.3.2) and need to build a
varchar array from a varchar column in the source table.

INSERT into X (ArrayCol) select oldval from Y;

gets a type error, but you can't cast to an array.

INSERT into X (ArrayCol[1]) select oldval from Y;

doesn't work either.

INSERT into X (ArrayCol) select '{"' || oldval || '"}' from Y;

also doesn't work.

There doesn't appear to be a to_array function.

Any suggestions?
--
Mike Nolan