fix error when use lib is used dynamic variables

I ran into an issue where lib::xi was crashing:

    Empty compile time value given to use lib at .//shubagooba/vhosts.d/server.lbl.gov/cgi-bin/sgd/f.pl line 6.
    Empty compile time value given to use lib at .//shubagooba/vhosts.d/server.lbl.gov/cgi-bin/sgd/f.pl line 7.
    Use of uninitialized value $_ in hash element at /Users/ben/perl5/perlbrew/perls/perl-5.18.1/lib/site_perl/5.18.1/lib/xi.pm line 34.
    BEGIN failed--compilation aborted at .//shubagooba/vhosts.d/server.lbl.gov/cgi-bin/sgd/f.pl line 10.
    make: *** [check] Error 255

It was due to some code that looked like this:

    # These should be set in the web server or environment
    use lib $ENV{BIOPERL_MODULE_PATH};
    use lib $ENV{INSITU_MODULE_PATH};

The supplied patch fixes the issue for me.