[R] What is wrong with this code?

[Cable, Samuel B Civ USAF AFMC AFRL/RVBXI]

Here it is:

read.inputs<-function(infile) {

   for (counter in 1:length(input.list)) {
      seek(infile,where=0,origin='start')
      newline<-readLines(infile,n=1)
      while(length(newline)>0) {
 
if(!is.na(grep(as.character(input.list[[counter]][1]),newline)[1])) {
          break
        }
        newline<-readLines(infile,n=1)
      }
      if (length(newline)>0) input.list[[counter]][2](infile)
   }

}

Conceptually, it is pretty simple:  I just want to read through a short
file, looking for several key words ('input.list[[counter]][1]').  If
one of these words is found, the reading loop is exited and the function
appropriate to found word ('input.list[[counter]][2]') is called.

The code stops running and returns an error of "attempt to apply
non-function" the very first time it hits the "break" statement, which
seems to me to be the most innocuous part of the entire routine.
Putting in debug statements, it seems that it crashes right at "break".
Why on Earth would R not like a "break" statement?

Also, there must be a more elegant way to do character matching than the
"grep" thing I have kluged together.  Any ideas on that are welcome as
well.

Thank you very much for your help.