st: add zero to values of variable

["raoul reulen" <r.c.reulen@gmail.com>]

Hi,

I have a variable  which has 2-digit values and 3-values. I would like
to change all 2-digit values into 3 digits  by adding a zero. How can
I do this? Thanks.

Raoul
see example below

the list of values looks like this:

12
148
456
21
364
390

and I would like to add a zero to the third and fourth values.
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