perldoc -f say
...
"say" is available only if the "say" feature is enabled or if it
is prefixed with "CORE::". The "say" feature is enabled
automatically with a "use v5.10" (or higher) declaration in the
current scope.
So you could add
use v5.10; # or higher
...
or
use feature qw(say);
...
or
$_ = 'My name is Paquito';
CORE::say if /My name is/;
s/Paquito/Paquita/;
tr/A-Z/a-z/;
CORE::say;
Had you add use strict; the following warning would have been issued hinting that say is unknown:
Bareword "say" not allowed while "strict subs" in use at ./say.pl line
+ xyz.