Sounds like some kind of version problem. Here's from BerkeleyDB.xs:

int has_heap()
    CODE:
#ifdef AT_LEAST_DB_5_2
        RETVAL = __heap_exist() ;
#else
        RETVAL = 0 ;
#endif
[download]

So __heap_exist() gets called only if AT_LEAST_DB_5_2 is set (presumably because it's not there in older lib versions) and it's set in your compilation where it shouldn't. Maybe the configuration script finds a newer version of the library on your system but then you're linking against the old one?