use strict;
use warnings;

my %data;
while (<DATA>) {
   chomp;
   my ($f,$x,$y) = split /\s+|,/;
   push @{ $data{$f}{$x} }, $y;
}

my @data;
my $order = +1;
for my $f (sort keys %data) {
   my $xs = $data{$f};
   for my $x (sort { $a <=> $b } keys %$xs) {
      my $ys = $xs->{$x};
      push @data, map [ $f, $x, $_ ],
                  sort { $order * ( $a <=> $b ) }
                  @$ys;
      $order *= -1;
   }
}

print("$_->[0] $_->[1],$_->[2]\n") for @data;

__DATA__
...