Note that your second example doesn't test for an object but for an object or a package name and Perl considers most strings that don't contain control characters to be package names. This is easy to fix:

sub selfcontrol {
  my $self = shift;
  return $self if ref($self) && eval {$self->can("can")};
  carp "diem";
}
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        - tye (but my friends call me "Tye")