How to group repeated values ​​in a table

For other operations, such as counting the number of times duplicated, that might take quite a bit more effort.  Only one kind of solution is below:

a!forEach(
    items: union(local!list, local!list),
    expression: concat(
        fv!item,
        ":  ",
        length( wherecontains(fv!item, local!list) )
    )
)

Wherecontains spits out an index number for every time specified value appears in specified array, so if it's at position 5, 10, and 12, output is {5,10,12}.  So the length of that output is the number of times that value appears in the array.  You remove duplicates in the items definition so you don't have "Steve:5, Steve:5, Steve:5, Jeff: 1, Steve:5, Steve:5".

For other operations, such as counting the number of times duplicated, that might take quite a bit more effort.  Only one kind of solution is below:

a!forEach(
    items: union(local!list, local!list),
    expression: concat(
        fv!item,
        ":  ",
        length( wherecontains(fv!item, local!list) )
    )
)

Wherecontains spits out an index number for every time specified value appears in specified array, so if it's at position 5, 10, and 12, output is {5,10,12}.  So the length of that output is the number of times that value appears in the array.  You remove duplicates in the items definition so you don't have "Steve:5, Steve:5, Steve:5, Jeff: 1, Steve:5, Steve:5".

Thank you very much for your answer, how could I relate each user with its corresponding value? 
For example I need to assign the corresponding user:
James: 4,5,6
Jeff: 1,2,3
Mike: 7,8,9

Currently the values come out like this: 

Santiago: 1,2,3,4,5,6,7,8,9 
Jeff: 1,2,3,4,5,6,7,8,9 
Mike: 1,2,3,4,5,6,7,8,9