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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
He is using Regex (Regular Expression) to match the conditions required. Regex is really powerful, but can be a pain in the ass to work with sometimes. But it's a clever solution :-)