my $v = 'DA39A3EE5E6B4B0D3255BFEF95601890AFD80709';
my $m = 'FFFF804020100804020100804020100804000102';
my $vb = unpack 'B*', pack 'H40', $v;
my $mb = unpack 'B*', pack 'H40', $m;
my $rb = $vb & $mb;
print unpack 'H*', pack 'B*', $rb;

da39804000000804020100800020100004000100