For backward compatibility, the features that involve a new keyword need to be enabled explicitly, either via use 5.010; or use feature ':5.10'; or use feature qw/say switch state/;

In onliners, using -E instead of -e also enables all new features: 

perl -wE 'say 42'

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In reply to Re: wondering why does 5.10 features are not working by moritz
in thread wondering why does 5.10 features are not working by Anonymous Monk

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