Validating user-input to be inserted in regular expressions

Hi all,

I would like to take user input, which should be interpreted literally, and
put it inside a regular expression, something like

select * from files where path ~ (USER_INPUT || '.*')

How should I escape the user input? I mean: I know that I must insert double
backslashes before special characters (in the sense of regular expressions)
but how to know what these special characters are? Should I find every
possible character in the documentation for regular expressions? Is there a
safer way?

Thanks

Vincenzo Ciancia

--
Please note that I do not read the e-mail address used in the from field but
I read vincenzo_ml at yahoo dot it
Attenzione: non leggo l'indirizzo di posta usato nel campo from, ma leggo
vincenzo_ml at yahoo dot it