How do I create a regex for ipaddress to be used with other patterns in PL SQL

I need to write a regular expression in order to be able to match the following patterns:

IF:en0 

IF:en0:10.94.80.78

IF:en11

IF:en11:10.94.80.78

The regular expression i wrote in 开发者_StackOverflow中文版PL SQL was

IF REGEXP_LIKE(input_str,
'^IF:en([0-9])([:]?)((25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})$') then  
  DBMS_OUTPUT.PUT_LINE('Match');
END IF;

This works fine. But I want to know if there is a way in which I can make the pattern for ip address

((25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})

as a variable above and use something like

ipaddrpattern :=
  '((25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})';

IF REGEXP_LIKE(input_str,
'^IF:en([0-9])([:]?)||ipaddrpattern||$') then  
  DBMS_OUTPUT.PUT_LINE('Match');
END IF;

I tried the above but didn't work. Can someone please help me with the syntax?

You might want to concatenate your pattern :)
Use

'^IF:en([0-9])([:]?)' || ipaddrpattern || '$') then

instead of

'^IF:en([0-9])([:]?)||ipaddrpattern||$') then

Your current implementation would match

'IF:en1ipaddrpattern'