+is(join(":", map "[$_]", @foo), '[]');
+
+# again with magic
+{
+ my @a = (1..3);
+ @foo=(); push @foo, $_ for undef..$#a;
+ is(join(":", @foo), '0:1:2');
+}
+{
+ my @a = ();
+ @foo=(); push @foo, $_ for $#a..undef;
+ is(join(":", @foo), '-1:0');
+}
+{
+ local $1;
+ "2" =~ /(.+)/;
+ @foo=(); push @foo, $_ for undef..$1;
+ is(join(":", @foo), '0:1:2');
+}
+{
+ local $1;
+ "-2" =~ /(.+)/;
+ @foo=(); push @foo, $_ for $1..undef;
+ is(join(":", @foo), '-2:-1:0');
+}
+{
+ local $1;
+ "B" =~ /(.+)/;
+ @foo=(); push @foo, $_ for undef..$1;
+ is(join(":", map "[$_]", @foo), '[]');
+}
+{
+ local $1;
+ "B" =~ /(.+)/;
+ @foo=(); push @foo, $_ for ""..$1;
+ is(join(":", map "[$_]", @foo), '[]');
+}
+{
+ local $1;
+ "B" =~ /(.+)/;
+ @foo=(); push @foo, $_ for $1..undef;
+ is(join(":", map "[$_]", @foo), '');
+}
+{
+ local $1;
+ "B" =~ /(.+)/;
+ @foo=(); push @foo, $_ for $1.."";
+ is(join(":", map "[$_]", @foo), '');
+}