Check the lexical scoping of the say keyword.
(The actual behaviour is tested in t/op/say.t)

__END__
# No say; should be a syntax error.
use warnings;
say "Hello", "world";
EXPECT
Unquoted string "say" may clash with future reserved word at - line 3.
String found where operator expected at - line 3, near "say "Hello""
	(Do you need to predeclare say?)
syntax error at - line 3, near "say "Hello""
Execution of - aborted due to compilation errors.
########
# With say, should work
use warnings;
use feature "say";
say "Hello", "world";
EXPECT
Helloworld
########
# With say, should work in eval too
use warnings;
use feature "say";
eval q(say "Hello", "world");
EXPECT
Helloworld
########
# feature out of scope; should be a syntax error.
use warnings;
{ use feature 'say'; }
say "Hello", "world";
EXPECT
Unquoted string "say" may clash with future reserved word at - line 4.
String found where operator expected at - line 4, near "say "Hello""
	(Do you need to predeclare say?)
syntax error at - line 4, near "say "Hello""
Execution of - aborted due to compilation errors.
########
# 'no feature' should work
use warnings;
use feature 'say';
say "Hello", "world";
no feature;
say "Hello", "world";
EXPECT
Unquoted string "say" may clash with future reserved word at - line 6.
String found where operator expected at - line 6, near "say "Hello""
	(Do you need to predeclare say?)
syntax error at - line 6, near "say "Hello""
Execution of - aborted due to compilation errors.
########
# 'no feature "say"' should work too
use warnings;
use feature 'say';
say "Hello", "world";
no feature 'say';
say "Hello", "world";
EXPECT
Unquoted string "say" may clash with future reserved word at - line 6.
String found where operator expected at - line 6, near "say "Hello""
	(Do you need to predeclare say?)
syntax error at - line 6, near "say "Hello""
Execution of - aborted due to compilation errors.