#!/usr/bin/perl 
use strict;
use warnings;  

sub mysub (\@) {

    my $arg = $_;
    print ref $arg."\n";

}

my (@array, %hash, $scalar);

mysub (\@array);
mysub (\%hash);
mysub (\$scalar);

mysub (@array);    # This is the only one which compiles
mysub (%hash);
mysub ($scalar);

mysub (qw(This is a list));