But a generic solution of suppressing warnings in foreign code is manipulating signal handler in %SIG.

I did it once and this might help here

               The routine indicated by $SIG{__WARN__} is called when 
+a
               warning message is about to be printed.  The warning me
+ssage is
               passed as the first argument.  The presence of a "__WAR
+N__"
               hook causes the ordinary printing of warnings to "STDER
+R" to be
               suppressed.  You can use this to save warnings in a var
+iable,
               or turn warnings into fatal errors, like this:

                   local $SIG{__WARN__} = sub { die $_[0] };
                   eval $proggie;
[download]

you may want search the archives for more examples of how to use this.