replace() function problem

Hi all,

I use replace function at psql prompt, but the result turns out to be
weired...
-------------8<--------------------------
twins=# select replace('%a', '  ', '  ');       replace
------------------------0x1.fe98800000001p+0
(1 row)
------------->8--------------------------

Why is that so? Is it a bug?

Thanks...

Frankie Lam