if ( SDL::Video::MUSTLOCK($screen_surface) ) {
    return if ( SDL::Video::lock_surface($screen_surface) < 0 ); #required for pixel operations
}

#USING pack

my $green = pack 'b*', '11111111000000000000000000000000';
substr( $surf32_matrix->[0][0], 0, 8 * 4, $green); #no change
#substr( $surf32_matrix->[0][0], 0, 8 * 4, 0xFF000000); segfault
substr( ${$surf32_matrix->[0][0]}, 0, 8 * 4, 0xFF000000); #no change
#$surf32_matrix->[0][0] = $green; SEGFAULT's cannot write to memory
${$surf32_matrix->[0][0]} = $green; #no change


SDL::Video::unlock_surface($screen_surface)
  if ( SDL::Video::MUSTLOCK($screen_surface) );