momo33:

You can certainly edit binary data in perl, and there are a number of ways to do it. I'll assume you know all about the vagaries of differences in binary data structures between CPU architectures, so I won't open that particular can of worms.

Anyway, it works for me. If you show the code, we may be able to tell you the problem. Here's how I tested it:

$ cat binary_snr.pl 
#!/usr/bin/perl
use strict;
use warnings;

my $binstr = join("", map { chr($_) } 0 .. 20);

my $search_1 = join("", map { chr($_) } 7 .. 11);
my $repl_1   = join("", map { 'A' }     7 .. 11);

if ($binstr =~ s/$search_1/$repl_1/) {
    print "Fixed first one\n";
}

print join(" ", map { ord($_) < 32 ? sprintf "0x%02x", ord($_) : $_ }
        split /|/, $binstr), "\n";

$ perl binary_snr.pl
Fixed first one
0x00 0x01 0x02 0x03 0x04 0x05 0x06 A A A A A 0x0c 0x0d 0x0e 0x0f 0x10 
+0x11 0x12 0x13 0x14

$
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.

Update: minor text update to "If you show" sentence.