Question about indexes and operator classes

Hi,

I actually have several questions on indexes and operator classes:

1) What is the difference between *varchar_pattern_ops* and *
varchar_text_ops*?
They both appear to work similarly and in both cases the operands are cast
to
type TEXT when I look at the explain of the query.

2) Is there any pre-definded operator class for indexes with regular
expressions?

3) How do I define an index which would be invoked when querying with
regexps
in the WHERE-clause?

4) There appears to be no documentation of the included operator classes in
the
Postgresql documentation while the feature looks to me like its use cannot
be
emphasized enough.
Postgresql 9.1.7 has about 220 operator classes but very few of them are
even
mentioned in the manual. Oracle 11 apparently has no pre-defined operator
classes
(they call them "application domain indexes") and only includes a
documentation
on how to make them which is more or less around three corners and climbing
stairs
while balancing a water cup on your nose - this appears to me to be a very
big marketing advantage for Postgres over Oracle.

Should I post a bug report to the PGSQL-BUGS list against the documentation
?

Thanks,

R.