http://www.perlmonks.org?node_id=1020720


in reply to Unquoted string "say" may clash with future reserved word

The help for say says 

This keyword is available only when the "say" feature is enabled, or w
+hen prefixed with "CORE::"; see feature.
Alternately, include a "use v5.10" or later to the current scope.

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Perl ships with lots of documentation :) try perldoc

In Section Seekers of Perl Wisdom