vecor/list INSERT or UPDATE

SQL Gurus,

I want to update a specific set of rows in a column with a list or
vector.  Something like, 

UPDATE some_table SET col = [1 2 3 4 5] 
        WHERE some_condition_limits_to_five_rows;

but all I see UPDATE accepting is a scalar ("5") not a vector or list
("1 2 3 4 5")...is this even possible?

Thanks,
Adam


---
Here's a clearer (hopefully) but longer example

RPGSL_ROW_NUMBER   SOME_VARIABLE

4                       12
5                       13
6                       14
7                       14
8                       14

 
SOME_VARIABLE to be replaced with 1:5 using UPDATE so that we get


RPGSL_ROW_NUMBER   SOME_VARIABLE

4                       1
5                       2
6                       3
7                       4
8                       5






Adam