Magento 1.9 - use multiple Synonym for search term

Hi

I am using Magento 1.9.0.1 and use default Catalog Search. I have been looking for articles about using "Synonym" to improve search results. The search should work in a way if user search for

Caps = should bring result for 'Cap' and 'Caps'
Hat = should bring result for 'Hat' and 'Hats'
T-shirt = should bring result for 'Tshirt' and 'T-shirt'

We have multiple synonyms for each search term. We tried different ways to add multiple Synonyms i.e. comma seperated, semicolon seperated, with quotes, without quotes, etc. but it seems the search results are working only with single Synonym is entered.

Any help will be appreciated.

Thanks