if

if(Expr, Expr, [Expr])

Produces the value of it's 2nd argument if it's first argument is true, otherwise produces the value of it's third argument, or nothing if it has no third argument.

e.g.

if(
    cmp("lt", load("/volume"), 11),
    load("/normal_amp"),
    load("/this_one_goes_to_11")
)

If "/volume" is less than 11 then the value is "/normal_amp", otherwise the value is "/this_one_goes_to_11".

e.g.

if(cmp("eq", 11, load("/volume")), "huzzah!")

Produces "huzzah!" if /volume is 11, otherwise nothing.