quotemeta is both defined by s/(\W)/\\$1/ and by "being the function with which you escape strings in regexes", which means that in perl 5, a sequence of a backslash and a non-word-character will always literally match the non-word characters (because otherwise it would break too much existing code).

Sadly also no non-word-character can get a new meaning without a preceding backslash, because it would also break stuff.

So there remain only a few possible ways in which new features can be introduced syntactically:

• With modifiers that change the syntax
• By using one of the rare free escape sequences (\F, \T, \y, \Y)
• By constructs that are now syntactically not valid, because they don't make any sense (perhaps ({...}), previously (* ... ))

All of these don't quite help to clean up the syntax, though.