Comment/Uncomment lines based on variable - R

Having an R code like this:

for (i in 1:length(DV)){names(DV[[i]])<-paste("DV", substr(names(P2[[1+10*(i-1)]]),12,19), sep="_")}
for (i in 1:length(DW)){names(DW[[i]])<-paste("DW", substr(names(P2[[1+10*(i-1)]]), 12,19), sep="_")}

How to automatically comment/uncomment these lines based on a variable. For example:

var<-TRUE

if (var=TRUE) then {comment/uncomment lines 39:43}