[squid-users] helper output in logs

I'm using store_id_program and I want my program to ouput a Key/Value
pair so the value goes in the logs

I tried with "log" and "tag" keys and using "%[et" and "%[ea" in
LogFormat but it didn't worked.

There's a generic Key/Value handling or each helper needs a special
support ?

-- 
Alfrenovsky