Variable length look-behind

Question

Is there any elegant solution to build a variable length look-behind regex such as this one ?

/(?<=eat_(apple|pear|orange)_)today|yesterday/g;
         


        

Answer 1

How about:

(?:(?<=eat_apple_)|(?<=eat_pear_)|(?<=eat_orange_))(today|yesterday)

A little bit uggly, but it works.