package Foo; 
use Bar;
1;

##</code><code>##

package Bar; 
0;

##</code><code>##

use Test::More tests => 2;

for (1 .. 2) {
    eval "require Foo";
    ok( $@, "Saw error loading Foo" );
}

##</code><code>##

1..2
ok 1 - Saw error loading Foo
not ok 2 - Saw error loading Foo
#   Failed test 'Saw error loading Foo'
#   at check_foo.pl line 5.
# Looks like you failed 1 test of 2.

##</code><code>##

my %have_module;
sub have_module {
    my $mod = shift;
    if ( ! exists $have_module{$mod} ) {
        $have_module{$mod} = eval "require $mod";
    }
    return $have_module{$mod};
}