Algorithm::Loops's NestedLoops handles this easily. I added extra arguments to function because function had no way of knowing what each argument was. (Was the first argument a x_pos? a y_pos? etc)

use Algorithm::Loops qw( NestedLoops );

my %params = (
  x_pos => [1..10],
  y_pos => [-5..5],
  z_pos => [0..15],
  spin  => [0, 1],
  neato => [1..10],
);

my @keys = keys %params;

NestedLoops(
   [ @params{@keys} ],
   sub { function(map { $keys[$_], $_[$_] } 0..$#keys) }
);

sub function {
   my %args = @_;
   print(join(', ', map { "$_ => $args{$_}" } keys %args), "\n");
}
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Update: You have since indicated you didn't care about the names, so the above simplifies to:

use Algorithm::Loops qw( NestedLoops );

my @params = (
  [1..10],
  [-5..5],
  [0..15],
  [0, 1],
  [1..10],
);

NestedLoops(\@params, \&function);

sub function {
   print(join(', ', @_), "\n");
}
[download]

I bet you didn't expect the solution to be one line long :)