> rule TOP
> & <alpha>*
> & <!abc>
The & syntax is specced, but it's not yet implemented in Rakudo.
But note that <!abc> is a zero-width assertion, so your example regex
matches at the start of a string, if it does not begin with 'abc'.
Since you anchor it to the end of string too, it can only ever match the
You can achieve the same with just ^$.
If you want to match an alphabetic string which does not include 'abc'
anywhere, you can write this as
^ [ <!abc> <alpha> ]* $