ActivePerl on Windows always (or at least with Perl 5.005) defines a function Win32::BuildNumber(), so you can check it at runtime:
if (defined &Win32::BuildNumber) {
say "This is ActivePerl";
}
else {
say "This is NOT ActivePerl";
}
ActivePerl , ActivePerl::BUILD(). ActivePerl 5.8.7 build 814, .