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

__END__
# No switch; given should be a bareword.
use warnings; no warnings 'experimental::smartmatch';
print STDOUT given;
EXPECT
Unquoted string "given" may clash with future reserved word at - line 3.
given
########
# No switch; whereso should be a bareword.
use warnings; no warnings 'experimental::smartmatch';
print STDOUT whereso;
EXPECT
Unquoted string "whereso" may clash with future reserved word at - line 3.
whereso
########
# No switch; but continue is still a keyword
print STDOUT continue;
EXPECT
Can't "continue" outside a whereso block at - line 2.
########
# Use switch; so given is a keyword
use feature 'switch'; no warnings 'experimental::smartmatch';
given("okay\n") { print }
EXPECT
okay
########
# Use switch; so whereso is a keyword
use feature 'switch'; no warnings 'experimental::smartmatch';
given(1) { whereso(1) { print "okay" } }
EXPECT
okay
########
# switch out of scope; given should be a bareword.
use warnings; no warnings 'experimental::smartmatch';
{ use feature 'switch';
  given (1) {print "Okay here\n";}
}
print STDOUT given;
EXPECT
Unquoted string "given" may clash with future reserved word at - line 6.
Okay here
given
########
# switch out of scope; whereso should be a bareword.
use warnings; no warnings 'experimental::smartmatch';
{ use feature 'switch';
  given (1) { whereso(1) {print "Okay here\n";} }
}
print STDOUT whereso;
EXPECT
Unquoted string "whereso" may clash with future reserved word at - line 6.
Okay here
whereso
########
# C<no feature 'switch'> should work
use warnings; no warnings 'experimental::smartmatch';
use feature 'switch';
given (1) { whereso(1) {print "Okay here\n";} }
no feature 'switch';
print STDOUT whereso;
EXPECT
Unquoted string "whereso" may clash with future reserved word at - line 6.
Okay here
whereso
########
# C<no feature> should work too
use warnings; no warnings 'experimental::smartmatch';
use feature 'switch';
given (1) { whereso(1) {print "Okay here\n";} }
no feature;
print STDOUT whereso;
EXPECT
Unquoted string "whereso" may clash with future reserved word at - line 6.
Okay here
whereso