if(  ! ref($r)  ) {
    # no reference at all
} elsif(  ! UNIVERSAL::can($r,'can')  ) {
    # unblessed ref
} else {
    # blessed ref
}

##</code><code>##

    if(  ref($r)  &&  UNIVERSAL::can($r,'can')  ) {
        # blessed ref
    }

##</code><code>##

    if(  ref($r)  &&  eval { $r->can('can') }  ) {
        # blessed ref
    }