PL/pgSQL manual

Sorry for the last post, finger error.

Anyways, I find all types of example like this:

CREATE FUNCTION somefunc() RETURNS INTEGER AS

I'm looking for an example of a function that will prevent an insert
based on a pattern match. Is this possible and if so DO I need to return
something? I guess to sum to it up, I need a function that will match a
pattern and then a trigger that will not allow an insert based on what
that function matches.

I'm sure I am just making this harder than it really is...

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