I have a lot of product pages like this:
www.example.com/catalog001/item123
www.example.com/catalog002/item321
www.example.com/catalog002/item567
Every catalog and product(item) have its own numeric id.
Product pages are similar. Just different product image, price, title.
I tried to use Regular Expressions to set up original url pattern in Analytics Experiments:
www.example.com/catalog(\d+)?/item(\d+)?
Is there any way to set up original url pattern?
I'm not quite sure what you're asking. It sounds like you want to test many different product pages without setting up many different experiments, presumably to test two different product page layouts.
If so you can use relative urls in the experiments interface for that, there is no need for regular expressions. Create an experiment for one product page, select relative urls for the variations, enter a query string (?foo=bar) or fragment identifier (#foo=bar) that triggers the variation page, add experiment code to all the originals and the test will be enabled for all your product pages, not just the one url you entered in the interface.
If you were after something else I suggest you re-word the question to explain the actual problem rather than your attempt to solve it.