#/usr/bin/perl

use strict;
use warnings;

{
local $SIG{__WARN__}="IGNORE";
warn '$SIG{__WARN__} was set to "IGNORE"!'; <=== appears
};
{
local $SIG{__WARN__}= sub {};
warn '$SIG{__WARN__} was set to sub {};!';  <=== doesn't appear
};