Difference between single pipe and double pipe in Raku Regex (| Vs ||)

Question

There are two types of alternation in Raku's regex: the | and ||. What is the difference ?

say 'foobar' ~~ / foo || foobar /  # ｢foo｣
say 'foobar' ~~ / foo | foobar /   # ｢foobar｣

Answer 1

• The || is the old alternation behaviour: try alternation from the first declared to the last

• The | try alternation from the longest to the shortest declarative atom. It is called the Longest Token Matching Spec strategy.

say 'foobar' ~~ / foo || foobar /  # ｢foo｣ is the first declared
say 'foobar' ~~ / foo | foobar /   # ｢foobar｣ is the longest token

More detailed answer in this post