DreamT:

This ought to give you a head start. However, you didn't specify your problem very well, as I have no idea what type of treemenu you're wanting. (Web? Tk? Windows? ...?) So the code builds a hash containing the structure of your treemenu. Just add the appropriate code in dumptree to build your menu in whatever UI you need.

Roboticus@Roboticus-PC ~
$ cat treemenu.pl
use strict;
use warnings;

my %menu;
my $hr;
while (<DATA>) {
  chomp;
  my @keys = split /\|/,$_;
  next if @keys < 1;
  $hr = \%menu;
  while (my $k=shift @keys) {
    $$hr{$k} = {} unless exists $$hr{$k};
    $hr = $$hr{$k};
  }
}

dumptree('', \%menu);

sub dumptree {
  my $indent = shift;
  my $hr = shift;
  for my $k (sort keys %$hr) {
    print $indent, $k, "\n";
    if (keys %{$$hr{$k}}) {
      dumptree($indent."  ", $$hr{$k});
    }
  }
}

__DATA__
CDs
Books|Adventure
Movies|Music
Books
Books|Sports
Movies
Movies|Adventure
Books|Drama
CDs|Classic


Roboticus@Roboticus-PC ~
$ perl treemenu.pl
Books
  Adventure
  Drama
  Sports
CDs
  Classic
Movies
  Adventure
  Music

Roboticus@Roboticus-PC ~
$
[download]

...roboticus