open my $in,  '<:raw', 'infile.dat' or die $!;
open my $out, '>:raw', 'outfile.dat' or die $!;
# reading with a bigger block size is much more efficient
# than byte by byte reading
local $/ = \1024;
while (<$in>) {
   my $copy = $in;
   $copy =~ s/\x00/\x17/g;
   print $out $copy;
}
close $in or die $!;
close $out or die $!;