open(FILE,"< f1.txt");
@linesf1=<FILE>;
close(FILE);
open(FILE,"< f2.txt");
@linesf2=<FILE>;
close(FILE);
foreach $linef1(@linesf1)
{
 $found=0;
 chomp($linef1);
 foreach $linef2(@linesf2)
 {
  chomp($linef2);
  if($linef2=~/ $linef1/)
  {
   print "$linef1--->$`\n";
   $found=1;
  }
 }
 if(!$found)
 {
  print "$linef1--->null\n";
 }
}