my $yes_no=my $add_line="";

sub yesno
    {
     $yes_no=uc($yes_no);	    
     if (($yes_no ne "Y") || ($yes_no ne "YES"))
        {
         close (TESTFILE); 
	 print "\nWrite operations complete - File closed\n";
         exit 1;
        }	 
    }

open(TESTFILE, ">>$logfile")||die("unable to open file\n");
while (1)
 {
  print "Enter line of text to add : ";
  $add_line=<STDIN>;
  print TESTFILE $add_line;
  print "Add another line? (Yes/No) :";
  yesno(chomp($yes_no=<STDIN>));
 }