Answer: Simplest regex would be <a[^>]*?>([^>]*?)</a> whitch matches properly formated HTML. 

I got lots of comments and questions about edge cases. My advice, do not overcomplicate ! Just voice out your assumptions and in the most cases you will be in a great shape. If you want to get a little more elaborate, throw in white space checking as <s*a[^>]*?>([^>]*?)</as*>

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