#! /usr/bin/perl

use strict;
use warnings;

my @sites = ('a', 'b', 'c');
my @servers = ('A', 'B');
my @data_type = ("X", "Y", "Z");

foreach my $site (@sites) {
    foreach my $server_type (@servers) {
        foreach my $data (@data_type) {
            #statements
        }
    }
}

sub cartesian {
    my @C = map { [ $_ ] } @{ shift @_ };
    foreach (@_) {
        my @A = @$_;
        @C = map { my $n = $_; map { [ $n, @$_ ] } @C } @A;
    }
    return @C;
}

my @sites = ('a', 'b', 'c');
my @servers = ('A', 'B');
my @data_type = ("X", "Y", "Z");

foreach (cartesian(@sites, @servers, @data_type)) {
    ($data, $server_type, $site) = @$_;
    print "$site $server_type $datan";
}

use Set::CrossProduct;

my @sites = ('a', 'b', 'c');
my @servers = ('A', 'B');
my @data_type = ("X", "Y", "Z");

my $cross = Set::CrossProduct->new(
    [ @sites, @servers, @data_type ]
    );

while( my $tuple = $cross->get ) {
    print "@$tuplen";
    }

use strict;
use warnings;

my %sites = (

    a => {
        A => {
            data_type => [ 'X', 'Y' ],
        }
    },

    b => {
        B => {
            data_type => [ 'Y', 'Z' ],
        }
    },

    c => {

    },
);

for my $site ( keys %sites ) {
    for my $server ( keys %{ $sites{ $site } } ) {
        for my $data ( keys %{ $sites{ $site }{ $server } } ) {
            my @data_types = @{ $sites{ $site }{ $server }{ data_type } };
            say "On site $site is server $server with $data @data_types";
        }
    }
}

while ( my ( $site, $site_info ) = each %sites ) {
    while ( my ( $server, $server_info ) = each %{ $site_info } ) {
        my @data_types = @{ $server_info->{data_type} };
        say "On site $site we have server $server with data types @data_types"
            if @data_types;
    }
}

for(my $i = 0; $i <= $#sites; $i++){
    for(my $j = 0; $j <= $#servers; $j++){
        for(my $k = 0; $k <= $#data_type; $k++){
            do_functions ...