checking shared libraries for non default loaders
Python, Perl, and other interpreted languages do load things dynamically using dlopen(). (This is not the same thing as replacing the standard loader; they are still using that, and in fact dlopen() is a hook into the standard loader on ELF-based systems.)
There is no standard registry for loadable modules. Python uses its own rules to determine where extension modules can be loaded from (look at sys.path), including those which have associated shared objects. Perl uses different rules. Apache uses still different rules, etc.
So to summarize the answers to your questions:
not exactly
no