$success = 0;
open(FILE,"dumptape.log") or die ("Could not open file");
while(<FILE>) {
  if (/Dump phase number 3/) {
    print;
    <FILE> for (1..2);
    print <FILE>;
    $success = 1;
    last;
  }
}
if(!$success) { 
  print "Failed dump log\n"; 
  #do other failed dump log stuff here
}
close FILE;