use warnings;
print($^W, "\n");  # 0  XXX

##</code><code>##

{
   use warnings;
   print($^W, "\n");  # 0  XXX
}
{
   local $^W = 1;
   print($^W, "\n");  # 1  ok
}
{
   no warnings;
   local $^W = 1;
   print($^W, "\n");  # 1  XXX
}