hello
please, take a note about correct tabs in data when you will check this sample

#! /usr/bin/perl

use strict;
use warnings;

my $id = 0;
my $tabCntr;
my %parent;
my $parentId = 0;
$parent{0} = 0;

while (<DATA>) {
    chomp;
    $tabCntr = (s/\t//g || 0);
    $parent{$tabCntr} = ++$id;
    $parentId = $tabCntr?$parent{$tabCntr - 1}:0;
    print "id : $id, name : $_, parent $parentId \n";
}    

__END__
cat1
    cat1,sub1
        cat1,sub1,sub-sub1
        cat1,sub1,sub-sub1
            cat1,sub2
cat2
cat3
    cat3,sub1
[download]

result of the program

id : 1, name : cat1, parent 0
id : 2, name : cat1,sub1, parent 1
id : 3, name : cat1,sub1,sub-sub1, parent 2
id : 4, name : cat1,sub1,sub-sub1, parent 2
id : 5, name : cat1,sub2, parent 4
id : 6, name : cat2, parent 0
id : 7, name : cat3, parent 0
id : 8, name : cat3,sub1, parent 7
[download]