combination of 'textcat' and 'interval' in 7.2.

hi,

just a day back, i did upgrade to 7.2(from 7.1.2).

In my plpgsql functions, i did use(in 7.1.2) 
SELECT INTO <variable> interval(textcat (4, '' hours''));

But now, i do use (in 7.2)
SELECT INTO <variable> cast (textcat (4, '' hours'') as interval);

and it works.

is this a permanent fix? will it work in earlier and future releases?
Would like to get some links on migration of plpgsql functions from
7.1.x to 7.2?

Regards,
Bhuvaneswar.