regex to match repeated consonant

Question

How can I detect with a regex expression if the same consonant is repeated three times or more?

My idea is to match words like tttoo

Answer 1

You can use capture groups with back-references. This will capture repeating symbols:

/(
   ([\w])        ## second group is just one symbol
   \2            ## match symbol found in second groups
   \2+           ## match same symbol one or more times
)/x              ## x is just to allow inner comments

But not all regexp engines support back-references.