any better explanation of look ahead assertions

[ToddAndMargo]

Hi All,

Looking at:
    https://docs.perl6.org/language/regexes#Lookahead_Assertions
    https://docs.perl6.org/language/regexes#Lookbehind_assertions

I can't tell heads from tails.  Does anyone know of a better
reference/explanation for beginners?


Many thanks,
-T