How to release SET() in PgSQL?

Hello All!

I used MySQL for a long time. There is SET() conception.
I can define SET('one','two','three') and use that type:

CREATE TABLE "test" (
"a" SET('one','two','three')
};

And then:

SELECT * FROM test WHERE a = 'one';
or
SELECT * FROM test WHERE a like 'one,three';

How can I do it in PgSQL? I need it so much!

--
with respection Andrey Feofilactovich.
e-mail: feo(at)ttn(dot)ru, feo(at)feo(dot)org(dot)ru
ICQ: 28073807