When G_KEEPERR is used, any errors in the called code will be prefixed
with the string "\t(in cleanup)", and appended to the current value
-of C<$@>.
+of C<$@>. an error will not be appended if that same error string is
+already at the end of C<$@>.
+
+In addition, a warning is generated using the appended string. This can be
+disabled using C<no warnings 'misc'>.
The G_KEEPERR flag was introduced in Perl version 5.002.