my $filename='out.txt';
my $output  ='perl_output.txt';

if (-r $filename) {
  open(FILE, "< $filename");
  open(OUTPUT, "> $output");

  while(<FILE>) {
  chomp;
  if(/^(.*)Datasource:/){
     print OUTPUT "\n\n", $_, "\n";
     ...
     ...
  }
  close(FILE);
  close(OUTPUT);
  } 
  else{
     print("cant read file ",$filename,"\n");
  }