#! /usr/bin/perl -w

use strict;
use warnings;
use feature qw(say);

my $hoge = 1;
my @hoge = (0, 1, 2, 3);

my $ret = double(\$hoge);
say $$ret;
my @ret = double(\@hoge);
say join(
    ", ",
    @{ $ret[0] },
);

sub double {
    my $reference = shift;
    
    my $type = ref $reference;
    if ($type eq "SCALAR") {
        ${$reference} *= 2;
    }
    elsif ($type eq "ARRAY") {
        @{$reference} =
            map { $_ * 2 }
                @{$reference};
    }
    else {
        warn "something wrong";
    }
    return $reference;
}