Recursive SETOF function

I'm trying to port some TSQL to PLPGSQL. The DB has a table with a
recursive foreign key that represents a tree hierarchy. I'm trying to
re-create a TSQL function that pulls out all the ancestors of a given
node in the hierarchy.

I'm rather new to PLSQL and I have several questions.

1. In TSQL, I can assign a scalar to the result of query like so:
SET @var1 = (SELECT foo FROM bar WHERE bar(dot)uid=(at)var2)

How would I do this in PLSQL?

2. In TSQL the "result table" can be inserted into manually. IE:

CREATE FUNCTION foo () RETURNS @ttable TABLE( uid INTEGER) AS BEGIN
INSERT @ttable VALUES (1)
RETURN
END

Is there a way to manually insert rows into the result table in PLSQL?

What follows is my TSQL function if that helps give context.

CREATE FUNCTION svp_getparentproviderids (@child_provider INTEGER)
RETURNS @provider_ids TABLE ( uid INTEGER )
AS
BEGIN
DECLARE @cid AS INTEGER
IF (SELECT count(*) FROM providers WHERE uid =(at)child_provider) > 0
BEGIN
SET @cid = @child_provider
WHILE @cid IS NOT NULL
BEGIN
INSERT @provider_ids VALUES (@cid)
SET @cid = (SELECT parent_id FROM providers WHERE uid=(at)cid)
END
END
RETURN
END

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