this code will grab the root.zone file from NSI and give you a list of all the ICANN-sanctioned TLDs.

#!/usr/bin/perl -lw

use LWP::Simple;
use strict;

use vars qw($ROOT_ZONE);

$ROOT_ZONE = 'ftp://rs.internic.net/domain/root.zone';

my $data = get $ROOT_ZONE or die "Failed to fetch root zone\n";
my @lines = split /\r\n?|\n/, $data;
my %tlds;

for (@lines)
{
    # ignore all but nameserver (NS) records
    next unless /\s+IN\s+NS\s+/;

    # grab the first "column"
    my ($tld) = split ' ', $_, 2;

    # ignore entries for the root zone
    next if $tld eq '.';

    # strip off the trailing '.' and count the NS record
    ++$tlds{substr $tld, 0, -1};
}

print for sort keys %tlds;
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