I don't see what the execution speed measured on the benchmark website has to do with whether Python and Ruby occupy the middle ground. Except that that cleary shows that neither Python, Ruby or Perl are fast enough to be a substitute for C++ (or Java) in time critical code.

My (nearly uninformed) guess is that Python and Ruby can't compete with Perl on the low level aka sysadmin stuff but have the same limitations as Perl in really big projects