Regular Expression Mastery

Anchors

Ending anchor $

/ab$/

Attempt to match $ fails unless cursor is after the last character of the string
absinthe

             START             |a b s i n t h e
             ab                |a b s i n t h e       Yes!
             $                 <a b|s i n t h e       Nope
             START              a|b s i n t h e
             ab                 a|b s i n t h e       Nope
             START              a b|s i n t h e
             ab                 a b|s i n t h e       Nope
             START              a b s|i n t h e
             ab                 a b s|i n t h e       Nope

...

Match fails.
This simple case is of course optimized
In general, it really does do it this way