I think "Possessive Quantifiers" in perl5100delta Regular-expressions explains the version dependency. I am on 5.12.2, and here is what re shows:
$ perl -Mre=debug -e '/\d++/' Compiling REx "\d++" synthetic stclass "ANYOF[0-9][{unicode_all}]". Final program: 1: SUSPEND (7) 3: PLUS (5) 4: DIGIT (0) 5: SUCCEED (0) 6: TAIL (7) 7: END (0) stclass ANYOF[0-9][{unicode_all}] minlen 1 Freeing REx: "\d++" $ $ $ perl -Mre=debug -e '/\d+++/' Compiling REx "\d+++" Nested quantifiers in regex; marked by <-- HERE in m/\d+++ <-- HERE / +at -e line 1. $

In reply to Re^3: Perl Complains of Nested Quantifiers by toolic
in thread Perl Complains of Nested Quantifiers by sunmaz

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