our @array; # package vaiable
@array = qw( foo bar );

sub foo{
        my $var = shift;
        my $href = shift;
        my @array = $href->{pass_in} if defined $href and exists $href->{pass_in};
        push @array, $var;

        print "contents : @array\n";
}

print "outer scope - contents : @array\n";

foo(1);
foo(2);

print "outer scope - contents : @array\n";

__END__
outer scope - contents : foo bar
contents : 1
contents : 1 2
outer scope - contents : foo bar