Regular Expressions 101

Explanation
Pro

Group 1(\%(\w+(-|_)?(\w+)?)\%)+

+repeats the group contents below at least once:

\%the literal % (37₁₀ / 45₈ / 25₁₆)

Group 2(\w+(-|_)?(\w+)?)

\w+any word character, repeated at least once

Group 3(-|_)?

?repeats the group contents below at most once:

1st Alternative-

-the literal - (45₁₀ / 55₈ / 2D₁₆)

2nd Alternative_

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Group 4(\w+)?

?repeats the group contents below at most once:

\w+any word character, repeated at least once

\%the literal % (37₁₀ / 45₈ / 25₁₆)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Detailed match information will be displayed here automatically.

25 tokens

(\%(\w+(-|_)?(\w+)?)\%)+

New

<div class="%class_name%">
  This is my pet %breed% and it is %age% years old and has a %best-friend% named %friendName%.
</div>