+use Scalar::Vec::Util qw<vrot vcopy SVU_SIZE>;
+
+for ([ 1, 'offset', -1 ], [ 2, 'length', '-1' ]) {
+ my @args = ('1') x 4;
+ $args[$_->[0]] = $_->[2];
+ eval { &vrot(@args) }; my $line = __LINE__;
+ like $@, qr/^Invalid\s+negative\s+$_->[1]\s+at\s+\Q$0\E\s+line\s+$line/;
+}