$
$
$ cat lines.txt
Microsoft,IBM,Oracle,Apple
Windows 95,DB2,Oracle,MacBook
MS Excel,Fortran,Siebel,iPod
XBox,ATM,MySQL,iPad
Zune,Deep Blue,PeopleSoft,Pixar
$
$

$all_comp_products[0] = [ "Microsoft", [ "Windows 95", "MS Excel", "XBox", "Zune" ] ];

$all_comp_products[1] = [ "IBM", [ "DB2", "Fortran", "ATM", "Deep Blue" ] ];

$
$
$ cat -n lines.pl
     1  #perl -w
     2  # ##################################################################################################
     3  #
     4  #  For the data file that looks like this:
     5  #
     6  #  Microsoft,IBM,Oracle,Apple
     7  #  Windows 95,DB2,Oracle,MacBook
     8  #  MS Excel,Fortran,Siebel,iPod
     9  #  XBox,ATM,MySQL,iPad
    10  #  Zune,Deep Blue,PeopleSoft,Pixar
    11  #
    12  #  this Perl program creates a nested data structure @all_comp_products that looks like this:
    13  #
    14  #  $all_comp_products[0] = [ "Microsoft", [ "Windows 95", "MS Excel", "XBox",  "Zune"       ] ];
    15  #  $all_comp_products[1] = [ "IBM",       [ "DB2",        "Fortran",  "ATM",   "Deep Blue"  ] ];
    16  #  $all_comp_products[2] = [ "Oracle",    [ "Oracle",     "Siebel",   "MySQL", "PeopleSoft" ] ];
    17  #  $all_comp_products[3] = [ "Apple",     [ "MacBook",    "iPod",     "iPad",  "Pixar"      ] ];
    18  #
    19  # ##################################################################################################
    20
    21  my $file = "lines.txt";
    22  my $company;
    23  my $product;
    24  my @all_comp_products;
    25  my $idx = 0;
    26
    27  open (FH, "<", $file) or die "Can't open $file for reading: $!";
    28  while (<FH>) {
    29    chomp;
    30    if (/^Microsoft/) {
    31      foreach $company (split /,/) {
    32         push @all_comp_products, [ $company ];
    33      }
    34    } else {
    35      foreach $product (split /,/) {
    36         push @{${$all_comp_products[$idx]}[1]}, $product;
    37         $idx++;
    38      }
    39      $idx = 0;
    40    }
    41  }
    42  close (FH) or die "Can't close $file: $!";
    43
    44  # Now, we'll iterate through the nested data structure and display the data
    45  foreach my $item (@all_comp_products) {
    46    $company = $$item[0];
    47    print "Company  : $company\n";
    48    print "Products :\n";
    49    foreach my $prod (@{$$item[1]}) {
    50      print "           $prod\n";
    51    }
    52    print "=" x 40,"\n";
    53  }
    54
$
$

$
$ perl lines.pl
Company  : Microsoft
Products :
           Windows 95
           MS Excel
           XBox
           Zune
========================================
Company  : IBM
Products :
           DB2
           Fortran
           ATM
           Deep Blue
========================================
Company  : Oracle
Products :
           Oracle
           Siebel
           MySQL
           PeopleSoft
========================================
Company  : Apple
Products :
           MacBook
           iPod
           iPad
           Pixar
========================================
$
$