$ cat sum.cf
bundle agent main
{
  vars:
    "line_count" int => readintarray(
      "input",
      "${this.promise_dirname}${const.dirsep}input.txt",
      "#[^\n]*",
      " ",
      "inf",
      "inf"
    );
    "indices" slist => getindices( "input" );
  reports:
    "${with}" with => format( "%d", eval( "${input[${indices}][0]} + ${input[${indices}][1]}" ));
    DEBUG::
      "line_count is ${line_count}";
      "input is ${with}" with => storejson( "input" );
      "input[${indices}] is ${with}" with => storejson( "input[${indices}]" );
}

$ cat input.txt
2 3
2 2

$ cf-agent -KIf ./sum.cf
R: 5
R: 4