--------
#! /usr/bin/perl -l
print "Originally foo() is a " . ref(*foo{CODE});
print "Initializing foo()";
*foo = sub {print "hello"};
print "foo() is now a " . ref(*foo{CODE});
print "According to can, foo is " . main->can("foo");
print "Calling foo()";
foo();

print "Undefining foo()";
$x = *foo;
undef &$x;
print "foo() is now a " . ref(*foo{CODE});
print "According to can, foo is " . main->can("foo");
print "Calling foo()";
foo();

__END__
Originally foo() is a
Initializing foo()
foo() is now a CODE
According to can, foo is CODE(0x8175b24)
Calling foo()
hello
Undefining foo()
foo() is now a CODE
According to can, foo is CODE(0x8175b24)
Calling foo()
Not a CODE reference at - line 17
--------