Analytics Software

I have WHERE IN condition in Direct DB Request Query. In Dashboard Prompt, presentation variable I have string as default (Type Edit Box, I am not using LOV).

In direct request :
select * from table1 where column1 IN ( '@{somevar1}' )

In Dashboard prompt the string value for Presentation Var somevar1 is

'Tom','Bob','Harry'

But the above won't get resolved for correct WHERE IN query syntax. How do I escape the single quote? or what should I type in Dashboard prompt so that the
respective WHERE condition will be formed like

select * from table1 where column1 IN ( 'Tom','Bob','Harry' )

I tried backslash but did not work

Thanks