Concatenating two Text fields from the same tuple

Apologies if this is a repost - I tried sending it yesterday and haven'
t seen it in the forum yet.

I am currently writing a perl script to convert the string a user
supplies to a search engine into SQL. The user supplies a string in the
same foramt as google uses - e.g. "cat -dog" finds records containing
cat but not dog.

The code i have written works well but i have just realised that if (
unknown to the user) the DB needs to search across more than one
attribute, a number of problems arise. For the above query the code
currently outputs WHERE head ILIKE '%cat%' AND head NOT ILIKE '%dog%'
OR body ILIKE '%cat%' AND body NOT ILIKE '%dog%';

which is equivalent to:
WHERE ( attr1 ILIKE '%cat%' AND attr1 NOT ILIKE '%dog%') OR ( attr2
ILIKE '%cat%' AND attr2 NOT ILIKE '%dog%');

This gives undesired behaviour - if 'cat' is found in the attr1 , and '
dog' is not found in attr1 of then the tuble is returned, even if dog
is found in attr2 of the tuple.

What is really wanted is: WHERE ( attr1 ILIKE '%cat%' OR attr2 ILIKE '%
cat%' ) AND attr1 NOT ILIKE '%dog%' AND attr2 NOT ILIKE '%dog%;

Question1 1: Is there already a google style search string parser out
there somewhere?

Question 2: If not - is it possible for me to concatenate attr1 and
attr2 before i do the search as this would remove the logic problems. (
and if it is possible - is it efficient?)

Question 3: If its not possible to concatenate them - any other
sugestions?!

Thanks!