Hi,
No, that is not enough, I like to overwrite the functions global regardless of the namespace.
So that this work:

*CORE::GLOBAL::system = sub { print "system\n" };
*CORE::GLOBAL::chdir = sub { print "chdir\n" };
*CORE::GLOBAL::glob = sub { print "glob\n" };
package xyz;
glob; chdir; system
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