Document another case when the "not imported" warning is used

The minimal example:

  use strict;
  { our $x; }
  print $x;

1 files changed, 2 insertions, 1 deletions

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 98d159dc21..88df948505 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -7598,7 +7598,8 @@ being executed, so its $a is not available for capture.
 that you apparently thought was imported from another module, because
 something else of the same name (usually a subroutine) is exported by
 that module.  It usually means you put the wrong funny character on the
-front of your variable.
+front of your variable. It is also possible you used an "our" variable
+whose scope has ended.
 
 =item Variable length lookbehind not implemented in regex m/%s/