;cperl-mode.el: Avoid false positives when parsing new Perl syntax

;cperl-mode.el: Avoid false positives when parsing new Perl syntax

* lisp/progmodes/cperl-mode.el (cperl--package-for-imenu-rx)
(cperl--class-for-imenu-rx): avoid false positives when collecting
imenu entries
* lisp/progmodes/cperl-mode.el (cperl-init-faces): avoid false
positives when detecting package names

* test/lisp/progmodes/cperl-mode-tests.el
(cperl-test-imenu-index): Add test verifying that $class_false is
not shown as a class _false

* test/lisp/progmodes/cperl-mode-resources/grammar.pl: Add a line
containing a false positive "$class_false"