How to detect if a text body contains forbidden words

I am using a modified version of the old formmail.pl script on my
website to get information requests mailed to me.
I have modified the script to NOT send email other than to two fixed
(hardcoded) addresses (myself and our sales dept). I had to do this
becvause spammers started to use my request pages as spam entry
points.

Now the spammers have advanced and are filling the fields with html
links in the hope that someone will click the links...

So I want to expand the script to block sending altogether if the body
contains forbidden words like 'href=' or 'http://'.

But I have no clue as regards PERL programming so I would like to get
some help in this.

I have a form field called 'Feedback' that is loaded with the contents
of a text box on my page. This text block is what I want to check for
the forbidden words and either modify the subject of the outgoing
email by adding something like '*** SPAM ***' to it or else not send
the email at all if forbidden words are found.

I think that the textbox contents can be retrieved by the following
function:
$CONFIG{'Feedback'}

What I would like to do is to add a new function right before the mail
send call inside the main procedure which could set an error if the
feedback contains the forbidden words.

The main procedure now looks like this:


# Check Referring URL
&check_url;

# Retrieve Date
&get_date;

# Parse Form Contents
&parse_form;

# Check Required Fields
&check_required;

# Return HTML Page or Redirect User
&return_html;

# Send E-Mail
&send_mail;

I would like to have a checking procedure right in front of
&send_mail, which will fail the script if the forbidden words are
present.

Any clues as to how to do this?

Bo Berglund