sub tee_print { print MYLOGFILE $_[0]; print $_[0] }
eval {
    local $SIG{__WARN__} = \&tee_print;
    my $h = MyModule->new(PrintHandler => \&tee_print);
    $h->method($params) or tee_print("oops: " . $h->errstr());
};
if ($@) { tee_print("error: $@") }