You can use eval(Meta.parse("$(v1)at()")), for example.
However, this sounds like a classic XY problem, in which you are reaching for the wrong tool for the job. What are you ultimately trying to accomplish?
In general, you almost never need to pass functions or expressions as strings — Julia has much better ways to deal with functions as variables. See also How one can evaluate @printf to be returned to a value - #6 by stevengj