Check feature bundles.

__END__
# Standard feature bundle
use feature ":5.10";
say "Hello", "world";
EXPECT
Helloworld
########
# Standard feature bundle, no 5.11
use feature ":5.10";
say utf8::native_to_unicode(ord uc chr utf8::unicode_to_native(233));
EXPECT
233
########
# Standard feature bundle, 5.11
use feature ":5.11";
say utf8::native_to_unicode(ord uc chr utf8::unicode_to_native(233));
EXPECT
201
########
# Standard feature bundle, 5.11
use feature ":5.11";
use utf8;
say utf8::native_to_unicode(ord "\ué"); # this is utf8
EXPECT
201
########
# more specific: 5.10.0 maps to 5.10
use feature ":5.10.0";
say "Hello", "world";
EXPECT
Helloworld
########
# as does 5.10.1
use feature ":5.10.1";
say "Hello", "world";
EXPECT
Helloworld
########
# as does 5.10.99
use feature ":5.10.99";
say "Hello", "world";
EXPECT
Helloworld
########
# 5.9.5 also supported
use feature ":5.9.5";
say "Hello", "world";
EXPECT
Helloworld
########
# 5.9 not supported
use feature ":5.9";
EXPECT
OPTIONS regex
^Feature bundle "5.9" is not supported by Perl \d+\.\d+\.\d+ at - line \d+
########
# 5.9.4 not supported
use feature ":5.9.4";
EXPECT
OPTIONS regex
^Feature bundle "5.9.4" is not supported by Perl \d+\.\d+\.\d+ at - line \d+
########
# 5.8.8 not supported
use feature ":5.8.8";
EXPECT
OPTIONS regex
^Feature bundle "5.8.8" is not supported by Perl \d+\.\d+\.\d+ at - line \d+
########
# :default
BEGIN { *say = *state = *given = sub { print "custom sub\n" }; }
use feature ":default";
say "yes";
state my $foo;
given a => chance;
EXPECT
custom sub
custom sub
custom sub
########
# :default and $[
# SKIP ? not defined DynaLoader::boot_DynaLoader
no feature;
use feature ":default";
$[ = 0;
$[ = 1;
EXPECT
Assigning non-zero to $[ is no longer possible at - line 5.
########
# "no feature"
use feature ':5.16'; # turns array_base off
no feature; # resets to :default, thus would turn array_base on, if it still existed
$[ = 0;
$[ = 1;
EXPECT
Assigning non-zero to $[ is no longer possible at - line 5.
########
# "no feature 'all"
no feature ':all'; # turns array_base (and everything else) off
$[ = 1;
EXPECT
Assigning non-zero to $[ is no longer possible at - line 3.
########
# NAME $^H accidentally enabling all features
eval 'BEGIN { $^H |= 0x1c020000 } $_ = evalbytes 12345';
print $_||$@;
EXPECT
Number found where operator expected at (eval 1) line 1, near "evalbytes 12345"
	(Do you need to predeclare evalbytes?)
syntax error at (eval 1) line 1, near "evalbytes 12345"