The question mark is a quantifier 

$ perl -le " qr{\d****} "
Nested quantifiers in regex; marked by <-- HERE in m/\d** <-- HERE **/
+ at -e line 1.

$ perl -le " qr{(?#an error follows)****} "
Quantifier follows nothing in regex; marked by <-- HERE in m/(?#an err
+or follows)* <-- HERE ***/ at -e line 1.

$ perl -le " qr{?} "
Quantifier follows nothing in regex; marked by <-- HERE in m/? <-- HER
+E / at -e line 1.

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You need to learn to character class :) See perlrecharclass

Try  <token: punctuation>  ( [.,?!"';:\-&()\[\]]+ )

See also RFC: A walkthrough from JSON ABNF to Regexp::Grammars and The usage of <ALIAS=\IDENT> of Regexp::Grammars

In reply to Re: Quantifier follows nothing error in Regexp::Grammars (quantifier "?") by Anonymous Monk
in thread Quantifier follows nothing error in Regexp::Grammars by nathaniels

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