I wonder if tr might help you. Particularly, the c flag complements the characters specified so, you can get rid of anything that isn't a newline (0x0a) and the range of printable characters from space (0x20) through ~ (0x7e). Also include return (0x0d) if on Windows.

$ perl -le '
> $str = qq{\x00\x03abc xyz\n\x00\x00\x0912 34 56\x05\n};
> print for map sprintf( q{0x%02x}, ord ), split m{}, $str;
> print q{-} x 20;
> $str =~ tr{\x0a\x20-\x7e}{}cd;
> print for map sprintf( q{0x%02x}, ord ), split m{}, $str;'
0x00
0x03
0x61
0x62
0x63
0x20
0x78
0x79
0x7a
0x0a
0x00
0x00
0x09
0x31
0x32
0x20
0x33
0x34
0x20
0x35
0x36
0x05
0x0a
--------------------
0x61
0x62
0x63
0x20
0x78
0x79
0x7a
0x0a
0x31
0x32
0x20
0x33
0x34
0x20
0x35
0x36
0x0a
$
[download]

I hope this is helpful.

Cheers,

JohnGG

Update: Fixed typo.