My point is simply that Perl doesn't give you any guarantee except "we will try to parse it". Maybe you will hit the right case for the right version of Perl, who knows ? The Web is full of DDOS attack based on exponential PCREs.
With actual regular expression, the complexity is guaranteed.
Perl 6 gives you pretty good control over where to use backtracking and where not. It parses regular languages with a NFA or DFA, and can switch to a backtracking engine.
More details in https://www.apress.com/us/book/9781484232279 (sorry for the plug, wrote it myself).
'abc' ~~ m:ratchet/ .* c /
When writing grammars, use `token` which turns on `:ratchet` for you.