Found in a package body:
g_friday CONSTANT VARCHAR2(6) := 'Friday';
...then a couple of hundred lines later:
if to_char(business_date,'fmDay') = g_friday then ...end-of-week processing... else ...regular processing... end if;
Now that's flexible. If end-of-week processing is ever moved to the weekend, all you have to do is set g_friday := 'Saturday'.