my @data = (
  [ 123.7, 456.7 ],
  [ 564.7, 234.9 ],
);

for my $datum ( @data ) {
  my( $x, $y ) = @$_;
  $bins[ int $x ][ int $y ]++;
}

for my $x ( 0 .. $#bins ) {
  defined $bins[$x] or next;
  for my $y ( 0 .. $#{$bins[$x]} ) {
    defined $bins[$x][$y] or next;
    print "$x $y $bins[$x][$y]\n";
  }
}