Constrain a Specman list so it doesn't have identical values in consecutive elements

I want to generate list in Specman from a limited range and ensure that no two consecutive entries in the list have the same value so these would be OK

[1,0,1,0,1,0,1]
[2,1,3,1,3,2,1]
[100, 22, 50, 62, 100]

but these would not

[1,0,1,1,1,0,1]
[2,3,3,1,3,2,1]
[100, 22, 50, 50, 100]

I've tried to use unique() like so

mylist[mylist_len] : list of uint;
keep mylist.unique(it).size() == mylist.size()

and I can't just keep it using a scalar either

keep mylist.unique(it).size() == mylist_len

I also tried using keep on the entries like so

keep for each (i) in mylist {
  if (index > 0) {
    keep mylist[index] != mylist[index+1];
  };
};

It it matters I'm constraining the entries in the list like so:

keep for each (i) in mylist {
    i < mylist_limit;
  };

you can use 'prev' in a 'for each'.

keep for each (i) in mylist {
    i < mylist_limit;
    i != prev;
};