+=head1 WARNING
+
+DO NOT USE this pragma in scripts that have multiple
+L<threads|threads> active. The locale is not local to a single thread.
+Another thread may change the locale at any time, which could cause at a
+minimum that a given thread is operating in a locale it isn't expecting
+to be in. On some platforms, segfaults can also occur. The locale
+change need not be explicit; some operations cause perl to change the
+locale itself. You are vulnerable simply by having done a C<"use
+locale">.
+