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
# HINT_FEATURE_MASK | HINT_LOCALIZE_HH
eval 'BEGIN { $^H |= 0x3c020000 } $_ = evalbytes 12345';
print $_||$@;
EXPECT
Number found where operator expected (Do you need to predeclare "evalbytes"?) at (eval 1) line 1, near "evalbytes 12345"
syntax error at (eval 1) line 1, near "evalbytes 12345"
Execution of (eval 1) aborted due to compilation errors.