Name indirection can substitute only a name value. The second SET command in the following example returns an error message because of the context. When evaluating the expression to the right of the equal sign, Caché interprets @var1 as an indirect reference to a variable name, not a numeric value.

SET var1 = "5"  SET x = @var1*6

SET var1 = "var2",var2 = 5  SET x = @var1*6

http://docs.intersystems.com/cache20171/csp/docbook/DocBook.UI.Page.cls?KEY=GCOS_operators#GCOS_operators_indirection

This was reported in WRC 895607.