Thanks, that was a good hint. I tried to read the warning and strict bits from other packages, so I've to find a way to do it without explicit BEGIN blocks. The following thing works, but why ?!?

package Aa;
use warnings;
#no warnings 'void'; 
use strict;
#no strict 'refs';

package Bb;
#>> when you uncomment this, it wont work!!
#use strict;
#use warnings;
#<<
    
my $strict = eval('package Aa;my $h;BEGIN { $h = ${^H} };return $h;');
printf "use strict " . ($strict == 1794 ? 'yes' : 'no') . "\n";
my $warn = eval('package Aa;my $w;BEGIN { $w = ${^WARNING_BITS} };retu
+rn $w;');
printf "use warnings " . (unpack('b*', warnings::bits('all')) == unpac
+k('b*', $warn) ? 'yes' : 'no') . "\n";
[download]

This prints:

use strict = yes
use warnings = yes

till you use all-warnings ans all-stricts. Conclusion: it works fine and do what I want.

And by the way: in last few weeks I've see a lot of little perl wonders like this. I think, there must be a perl-good. Now I'm a believer :D