Regular Expression Mastery

Anti-Greed

Ungreedy Version

/a+?(a|b)/

aaab

             START             |a a a b
             a                 |a a a b         Yes!
             +                 <a|a a b
              |                <a|a a b         Nope
               a               <a|a a b         Yes!
               END             <a a>a b         Yes!

We reached END, so the match succeeds; it found the aa part of aaab
This time the non-greedy match was more efficient
But that's because it was lucky -- it happened to find a shorter match
When shorter matches exist, non-greedy may find them quickly
But if not, they are slower than their greedy counterparts.