how to test string against regular expression contained in postgresql database field?

Hi All,

I have a table which contains a field with regular expressions. I want
to test a given string against this field to obtain the resulting
records but I am doing something wrong and cannot find out what.

table
os_regexp os_name
------------- -----------
win.*9x windows
linux linux
etc...

select os_name from table where 'windows9x' ~ os_regexp;
ERROR: invalid regular expression: empty expression or subexpression.


Any help appreciated, Joe.