=item is_module_installed

Tries to guess whether a module is installed (yet) or not.

=cut

sub is_module_installed
{
    my $module_name = shift;
    my $mod = $module_name;
    $mod =~ s/-([\d\.]+\d).*$//;
    my $min_ver = $1;
    (my $mod_name = $mod) =~ s/-/::/g;
    $mod =~ s/(?:-|::)/\//g;
    $mod .= '.pm';
    eval { require $mod; 1} or return 0;

    if ($min_ver or scalar @_)
    {
        $min_ver ||= shift;
        $min_ver = normalise_version($min_ver);
        
        my $mod_ver = do {
            no strict 'refs';
            normalise_version(${"${mod_name}::VERSION"});
        };
        
        if ($mod_ver and $mod_ver lt $min_ver)
        {
            return 0;
        }
    }
    1
}

sub normalise_version
{
    my $version = shift;
    my @subs;

    if ($version =~ /\./)
    {
        @subs = split /\./, $version;
    }
    else
    {
        @subs = map { ord } split //, $version;
    }
    join '.', sprintf(join('', ("%03d")x@subs), @subs);
}

##</code><code>##

my @tarballs = grep {
    not is_module_installed($_);
} glob '*.tar*';