I have now decided to implement a (maybe temporary) solution, and it isn't that hard or kludgy as I thought : 
sub RecSize {
  # Returns the length of the data required by a string for unpack()
  # Variable length (with "*") will result in an error
  # Platform specific stuff like "i" and "I" also result in an error
  my( $Data ) = @_;
  my( $Result, $Len, $Repeat ) = 0;
  my %Size = (
              "a"=>1, # A string with arbitrary binary data, will be n
+ull padded.
              "A"=>1, # An ascii string, will be space padded.
              "b"=>1, # A bit string (ascending bit order, like vec())
+.
              "B"=>1, # A bit string (descending bit order).
              "h"=>1, # A hex string (low nybble first).
              "H"=>1, # A hex string (high nybble first).
              "c"=>1, # A signed char value.
              "C"=>1, # An unsigned char value.
              "s"=>2, # A signed short value.
              "S"=>2, # An unsigned short value.
              "n"=>2, # A short in "network" (big-endian) order.
              "N"=>4, # A long in "network" (big-endian) order.
              "l"=>4, # A signed long value.
              "L"=>4, # An unsigned long value.
              "v"=>2, # A short in "VAX" (little-endian) order.
              "V"=>4, # A long in "VAX" (little-endian) order.
              "q"=>8, # A signed quad (64-bit) value.
              "Q"=>8, # An unsigned quad value.
              "x"=>1, # A null byte.
              "Z"=>1, # A zero terminated string (will need byte count
+ !)
             );
  while ( $Data =~ s/([aAbBhHcCsSlLnNvVqQxZ])(\d*)// ) {
    $Repeat = $2 || 1;
    $Len = $Size{$1};
    if ($Len) {
      $Result += $Len * $Repeat;
    } else {
      $Result = undef;
      last;
    };
  };
  return $Result;
};
sub decodeRecord {
  my ($Value, $Records, @Names) = @_;
  my (@Values) = unpack( $Records, $Value );
  my (%Result);
  foreach my $Name (@Names) {
    $Result{$Name} = $Values[0] if ($Name);
    shift @Values;
  };
  return \%Result;
};

[download]
This code is then used as follows : 
$strMacBinaryHeader = "CZ64A4A4AAvvvaaNNVVvaA4A8VVaaN";
@nameMacBinaryHeader = (
     "ID", "filename", "filetype", "filecreator", "fileflags",
     undef, "yoffs", "xoffs", "fileid", "fileflags2", undef,
     "dataforklength", "resourceforklength", "creationdate",
     "lastmodified", "infolength", "fileflags3", "macbinary3id",
     undef, "totalunpackedlength", "secondaryheaderlength",
     "macbinary3requiredversion", "CRC"
     );sub decodeMacBinaryHeader {
  my ($Buffer) = @_;

  my $Result = &decodeRecord($Buffer, $strMacBinaryHeader, @nameMacBin
+aryHeader );

  roundUp( \$Result->{dataforklength}, 128 );

  return $Result;
};
 $HeaderSize = &RecSize($strMacBinaryHeader);
$Filename = shift || "../macicon/test/icon";
open FILE, "< $Filename" or die "Error opening \"$Filename\" : $!\n";
binmode FILE;
read FILE, $MacBinHeader, $HeaderSize;

$Header = decodeMacBinaryHeader($MacBinHeader);
$ResourceForkStart = $HeaderSize
                     + $Header->{secondaryheaderlength}
                     + $Header->{dataforklength};

&dump( $Header );

[download]
where &dump() is a simple routine that dumps a hash...

In reply to My current solution by Anonymous Monk
in thread How to organize file records by Corion

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