SOLUTION

CREATE GLOBAL TEMPORARY TABLE std_temp_table
(
 constraint_name varchar2(45)
)
ON COMMIT PRESERVE ROWS;
-- Insert.
INSERT INTO std_temp_table (constraint_name)
 WITH names
 AS
 (
 SELECT 'AB_C_COST_GRP_ID' FROM dual UNION ALL
 ...
 SELECT 'ZN_FR_ID' FROM dual UNION ALL
 SELECT 'ZN_SYST_ID' FROM dual
 )
 SELECT *
 FROM names;
SELECT owner, table_name, constraint_name, r_owner, r_constraint_name, status
FROM all_constraints
WHERE constraint_type = 'R' -- "Referential integrity"
 AND r_constraint_name IN
 (
 SELECT constraint_name
 FROM all_constraints
 WHERE constraint_type IN ('P', 'U') -- "Primary key" or "Unique"
 )
 AND owner NOT IN ('CTXSYS', 'MDSYS', 'SYS', 'SYSTEM', 'XDB')
 AND constraint_name NOT IN (SELECT constraint_name FROM std_temp_table);

takes around 6.5 seconds!!

The other variant, with a JOIN, takes around 7 seconds:

SELECT owner, table_name, ac.constraint_name, std_temp_table.constraint_name, r_owner, r_constraint_name, status
FROM all_constraints ac
FULL OUTER JOIN std_temp_table
 ON ac.constraint_name = std_temp_table.constraint_name
WHERE constraint_type = 'R' -- "Referential integrity"
 AND r_constraint_name IN
 (
 SELECT constraint_name
 FROM all_constraints
 WHERE constraint_type IN ('P', 'U') -- "Primary key" or "Unique"
 )
 AND owner NOT IN ('CTXSYS', 'MDSYS', 'SYS', 'SYSTEM', 'XDB')
 AND std_temp_table.constraint_name IS NULL;

PS- Both must be equivalent, simply not run enough times. So the choice then comes down to a question of readability...

... with 2,631 constraints names (= the known FK in our standard DB) which I then exclude from the listing (via the WHERE clause).

UPDATE -- Answer to pertinent questions...

... with 2,631 constraints names (= the known FK in our standard DB) which I then exclude from the listing (via the WHERE clause).

Is this what you need? Thx!!