How do you use variable names that shadow column names?

output.txt

> select foo()
column reference "bar" is ambiguous
LINE 1: SELECT          bar FROM foobar LIMIT 1
                        ^
DETAIL:  It could refer to either a PL/pgSQL variable or a table column.
QUERY:  SELECT          bar FROM foobar LIMIT 1
CONTEXT:  PL/pgSQL function foo() line 1 at SQL statement

sproc-variables.sql

CREATE TABLE foobar(bar integer);
CREATE FUNCTION foo(OUT bar integer) AS $$ 
BEGIN 
  SELECT INTO bar bar 
    FROM foobar 
    LIMIT 1; 
END;
$$ LANGUAGE plpgsql;

Aha, more information in https://www.postgresql.org/docs/current/static/plpgsql-implementation.html , including how to label declaration blocks to disambiguate. To disambiguate parameters, you can prefix them with the name of the function[1]:

SELECT INTO bar foobar.bar 
  FROM foobar
  WHERE foobar.bar = foo.bar
  LIMIT 1; 

(Also these are all awful variable/table/function names)