use strict;
use Carp;
use Scalar::Util qw(readonly);

sub ro {
	print "readonly($_[0])=".readonly($_[0])."\n";
	$_[0] = 'xxx';
}
eval { ro('lonely') } or print $@;
eval { ro(named => 4); } or print $@;
eval { ro(-named => 7); } or print $@;

for (1..5) { # to test whether changing $_[0] affects the literal
  eval { ro(-loop => 7); } or print $@;
}