quote string exactly as it is

Hello,

How can I quote a string *exactly* as it is? I tried using
quote_literal() but it doesn't return what I need in some cases.

E.g.

If my
string is: ss\\\ss

And I do:

select quote_literal('ss\\\ss');

I get:

E'ss\\ss' <-- My string now has E'' added and one backslash has been removed!

What I want to do is to pass a string to a custom made function. Since the
string can contain various metacharcters I need some way to pass this string
exactly as it is.

(For those who might be interested, the strings I'm working
with are FASTQ quality scores)

I'm using Postgresql 8.3 on Windows XP

Thanks
a lot!

Dario