$instok(100,100,999,46) would be more identicle to $addtok (minus the dont add if duplicate), 999 since that well always make it the last element. * i mean this for real examples of course since you could just got 100.100 for the above
-1 puts it one in from the end so i guess it just follows 0 would put it at the end, i use 999 since with the string limit u cant have even 500 items let alone 999, and 999 for me stands out as PUT IT AT THE END