But what do you mean "wrongly coded"? How should htonl() be defined?

Your htonl:

sub htonl {
  my $input = shift;
  my $output = unpack( 'N*', pack( 'L*', $input ) );
  return $output;
}
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1. First, takes the number and "packs it" (converts it to binary) as a signed long:

   Which means that the return from that first pack is 4 bytes and encoded in whatever byte-order (endianess) your current platform uses:

   $packed = pack 'l', 17;;
   
   print length $packed;;
   4
   
   print ord( substr $packed, $_, 1 ) for 0 .. 3;;
   17
   0
   0
   0
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   On my intel system, that means little-endian (the low byte comes first).

2. But then, you unpack (convert binary to ascii), those 4 bytes, treating them a big-endian long ('N'), resulting in:

   $unpacked = unpack 'N', $packed;;
   
   print length( $unpacked );;
   9
   
   print ord( substr $unpacked, $_, 1 ) for 0 .. 9;;
   50
   56
   53
   50
   49
   50
   54
   55
   50
   0
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   Resulting in a 9-byte ascii encode string containing the number: 285212672; which is meaningless.

   htonl() could be correctly coded as sub htonl{ pack 'l>', $_[0] }; if you see the need for wrapping a built-in function in a silly named wrapper :)

Similarly, you will need to fix your ntohl(); something like this: sub ntohl{ unpack 'l>', $_[0] } would suffice.

That may fix the second part of your problem.