There are a couple of ways... One is using odds to prevent/allow items from being selected.

But, thinking about this a different way, you can make groups with the name -1, 0, and 1, and grab a group by name--with your variable.

Each item and group/list is a property of its parent:

parent
  child1
  child2

You can grab child1 by using the code parent.child1. But also if you have a variable prop_name with the value "child1" you can use that to grab a property of that name using the code parent[prop_name]. Even if the variable's value is a number like -1, 0, or 1, you can use it the same way.

I've demonstrated both methods here: https://perchance.org/679qmltn63#edit

If I understand correctly, you have something like:

val
  -1
  0
  1

entries
  a
  b
  c
  d
  e
  f
  g
  h
  i
  j
  k
  l
  m

Then based on the val, you would have to select: (a) if val = -1, only from a to k, (b) from b to l, (c) from c to m.

Here is my solution: https://perchance.org/8horj02y80

First, we select the val, and then base the range from it. Since it is from 1-11, etc, we can have the base to be 2-12, then add (subtract) the modifier to have 1-11 for -1, 2-12 for 0, and 3-13 for +1, by having a min and max variables:

modOut
  Modifier: [mod = val.selectOne] | Min: [min = 2 + mod] | Max: [max = 12 + mod]

Then, to create a 'dynamic' range, we use JavaScript's Template Literals, to create a dynamic Perchance Shorthand List:

random = [`{${min}-${max}}`]

Essentially, the template literal would be evaluated first, so if we have min as 3 and max as 13, then it would be {3-13}, and then Perchance would evaluate that into a random number between that range.

We can now then use that value to select the item from our list, in which we can do in many ways:

• Via .selectAll[index-1] since the arrays are accessed with zero-start indexing.

entryOut
  Selection: [x = random.evaluateItem] | Entry: [entries.selectAll[x-1].upperCase]

• Via Dynamic Odds (What is on the demo generator) For the dynamic odds, we can just add them directly on the entry list:

entries
  a ^[x == 1]
  b ^[x == 2]
  c ^[x == 3]
  d ^[x == 4]
  e ^[x == 5]
  f ^[x == 6]
  g ^[x == 7]
  h ^[x == 8]
  i ^[x == 9]
  j ^[x == 10]
  k ^[x == 11]
  l ^[x == 12]
  m ^[x == 13]

where x is selected before selecting the entry:

entryOut
  Selection: [x = random.evaluateItem] | Entry: [entries.upperCase]

Thanks for these solutions - clearly I have a lot to learn about Perchance, and some of these techniques will be helpful with some things I want to do in the future. I just discovered Perchance within the last week and really finding it useful for some tools for gaming.

I came up with this solution after posting the question - I created a "showhead" and "showtail" variable and set them to 0 or 1 based on my input field value, then tagged just the first and last list entries with "conditional odds" based on that value - like

lastitem ^[showtail]