using = in a function

Hi all,

I was reading the doc's on functions when I came across this:

"
An assignment of a value to a PL/pgSQL variable or row/record field is
written as:

variable := expression;
"

and I realized, I didn't do that!  My assignments look like:

tmp = extract(minute from result);
if tmp > 30 then
    tmp = 60 - tmp;
    offset = tmp || ' minutes';
    result = result + offset;
else
    offset = tmp || ' minutes';
    result = result - offset;
end if;


Notice I just use = and not :=.

My question is, is there a difference?  It seems to work both ways, so
I'm a little confused.

Thanks,

-Andy