Plpgsql: Iterating through a string of parameters

I'm struggling with how to make plpgsql iterate through a list of numbers 
input as a text string, eg. "1438 2656 973 4208". I figure that I can use the 
regexp_split_to_array() function to make an array of the string, but can I 
iterate through an array with eg. a FOR loop?

regards,
-- 
Leif Biberg Kristensen
http://solumslekt.org/