My brain hurts with all this pack, unpack gibberish.
You have a simple situation.
I will attempt to explain: my @bytes = unpack ('C*',$buf); is the key thing you need to understand.

#!/usr/bin/perl;
use strict;
use warnings;
                        #     !     /     u     s     r     /    b    
+  i     n     /
my $buf = pack ('C*', (0x23, 0x21, 0x2F, 0x75, 0x73, 0x72, 0x2f, 0x62,
+ 0x69, 0x6E, 0x2f));

#  $buf is now a sequence of "characters" which are 8 bit unsigned num
+bers
#  Don't go all crazy with me about multi-byte characters
#  Here "C" means 8 bits, one byte

#  The ASCII characters corresponding to those numbers are:
#  #!/usr/bin/

# to get a particular characters or a group of characters
# from the $buf string, use substr()
#
# substr EXPR,OFFSET,LENGTH,REPLACEMENT
# substr() is often used in conjection with unpack to generate
# a particular numeric value with different byte ordering of say
# a 16 or 32 or 64 bit value

print substr($buf,3,3);  #prints: usr
print "\n";
print substr($buf,7,4);  #prints: bin/
print "\n";

# Now translate each byte in $buf into an array..
# Each 8 bit character will be a represented on my
# computer as a 64 bit signed value in an array of
# what are named "bytes"

my @bytes = unpack ('C*',$buf);

# @bytes is now an array of numbers!

# in decimal values:
print "Decimal Values of \@bytes\n";
print "$_ " for @bytes; print "\n";

# Now to print those bytes in character context:
print "Character values of \@bytes\n";
print chr($_) for @bytes; print "\n";

__END__
usr
bin/
Decimal Values of @bytes
35 33 47 117 115 114 47 98 105 110 47 
Character values of @bytes
#!/usr/bin/
[download]

Update:
I looked back over some code from 2001:
This modifies the header of a wave file.
- creates byte strings in the correct order ("little endian")
- then replaces, in 2 places, the 32 bit values in the buffer with new values
- then writes the buffer with the new size parameters

Hope this helps give you some ideas...
How to replace a 32 bit value in a binary buffer with a new value...
I might do it differently now, but after 18 years, this code still makes "sense"

my $rsize = pack("V4", $new_riff_size); # "V4" means Vax or Intel "lit
+tle endian"
substr($buff,4,4) = substr($rsize,0,4);
my $data_size = pack("V4", $new_data_size);
substr($buff,54,4)= substr($data_size,0,4);
print OUTBIN substr($buff,0,58);
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.