SQL & PL/SQL

Hey all,
I am a newbie to REGEXP and have an issue where I have 2 spatial tables, for each object in table1 and am doing an SDO_NN to find the nearest 2 objects in table2. I also have an address column for each spatial table. I am trying to compare address1 (from table1) to both addresses (address2 from table2) to find the most likely match candidate.
After reading about REGEXP it seemed to me the REGEXP_LIKE was most likely best way of achieving my matches.
What I have come up with works alot of times but not always and I don't quite understand it.

Here is an example where I don't understand what is going on where I used REGEXP_LIKE as this
REGEXP_LIKE(address1,replace(address2,' ','|'))

SELECT 
  id,  
  address1,
  address2,
  CASE
    WHEN address1=address2 THEN 'EXACT MATCH'
    WHEN REGEXP_LIKE(address1,replace(address2,' ','|')) THEN 'PROBABLE MATCH'
    ELSE 'NON MATCH'
  END AS TEST
FROM
  (
  SELECT
    1 ID, '930 OLD STEESE HWY' address1, '930 OLD STEESE HWY' address2
  FROM
    DUAL  
  UNION SELECT
    3 ID, '930 OLD STEESE HWY' address1, '920 OLD STEESE HWY' address2
  FROM
    DUAL    
  UNION SELECT
    3 ID, '930 OLD STEESE HWY' address1, '99 COLLEGE RD' address2
  FROM
    DUAL    
  UNION SELECT
    4 ID, '930 OLD STEESE HWY' address1, '80 5TH ST' address2
  FROM
    DUAL      
  );

RESULTS
ID ADDRESS1            ADDRESS2            TEST
-- ------------------  ------------------  --------------
1  930 OLD STEESE HWY  930 OLD STEESE HWY  EXACT MATCH
2  930 OLD STEESE HWY  920 OLD STEESE HWY  PROBABLE MATCH
3  930 OLD STEESE HWY  99 COLLEGE RD       NON MATCH
4  930 OLD STEESE HWY  80 5TH ST           PROBABLE MATCH

I am really confused as to the 4th line in the results?
Any thoughts and or suggestions?
Appreciate it!
Cheers,
Eric