By using expression rule i need to get the sample output

a!localVariables(
  local!a: { "a", "b", "c" },
  local!b: { 100, 200, 300 },
  joinarray(
    a!flatten(
      a!forEach(
        items: local!a,
        expression: a!localVariables(
          local!prevItem: fv!item,
          a!forEach(
            items: local!b,
            expression: concat(local!prevItem, "-", fv!item)
          )
        )
      )
    ),
    ","
  )
)

output: 

"a-100,a-200,a-300,b-100,b-200,b-300,c-100,c-200,c-300"