$ENV{PATH} = "/foo/bin:/bar/bin:$ENV{PATH}";
$ENV{LD_LIBRARY_PATH} = "/foo/bin:/bar/bin:$ENV{LD_LIBRARY_PATH}";
$ENV{PERL5LIB} = "/foo/lib:$ENV{PERL5LIB}";

use lib "/foo/lib";
use foo;
# if I comment the above line and 
# uncomment below, it works, but that is not what I want.
# print `perl -e 'use foo; print "success\n";'`;