>perl -w -MO=Deparse tmp.pl
BEGIN { $^W = 1; }
sub BEGIN {
    require 5.01;
}
use strict 'refs';
BEGIN {
    $^H{'feature_say'} = q(1);
    $^H{'feature_state'} = q(1);
    $^H{'feature_switch'} = q(1);
}
my(@x) = ('x', 1);
my $y = \@x;
say $#@ x [1];

##</code><code>##

say $#@ x [1];