nepos@blackbox:~$ corelist Scalar::Util

Scalar::Util was first released with perl 5.007003
nepos@blackbox:~$ corelist Scalar::Util::XS

Scalar::Util::XS was not in CORE (or so I think)
nepos@blackbox:~$ corelist Scalar::Util::PP

Scalar::Util::PP was first released with perl 5.010001