As I fruitlessly tried to explain to you privately, $SIG{__DIE__} is not appropriate here. $SIG{__WARN__} is required. Maybe if I post a test you can run... 

use strict;
use warnings;

$SIG{__DIE__} = sub {
  my $wn = shift;
  return if $wn =~ /Use of uninitialized value/i;    #Most annoying
  return if $wn =~ /name "(?:.+?)" used only once/i; #Very annoying
  warn $wn;
};

print 123 + undef, "\n";  # We want to hide this warning.
print 123 + 'abc', "\n";  # We want to see  this warning.

[download]

outputs 

Argument "abc" isn't numeric in addition (+) at 591379.pl line 12.
Use of uninitialized value in addition (+) at 591379.pl line 11.
123
123

[download]

If you change $SIG{__DIE__} to $SIG{__WARN__}, you get the desired output. 

Argument "abc" isn't numeric in addition (+) at 591379.pl line 12.
123
123

[download]

Update: Regarding your update, $SIG{} = sub { ... }; is no good either. It's a syntax error.

In reply to Re^2: Imposing no warnings xxx upon callback code? by ikegami
in thread Imposing no warnings xxx upon callback code? by BrowserUk

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