#you can use my to declare things even in the middle of a
#statement!
#the for loop slurps in all the lines in DATAFILE,
#provided you have opened it for reading.

foreach my $line (<DATAFILE>)
{
   $line =~ s/&+/&amp;/;

   # you can also use my (...) to declare many variables
   # at once
   my ($isbn, $ocln, $title, $author, $call_number)
     = split(/\t/, $line);

   # you'll likely have different defaults for cases where
   # fields are undefined
   $isbn='' unless defined($isbn);
   $ocln='' unless defined($ocln);
   $title='' unless defined($title);
   $author='' unless defined($author);
   $call_number='' unless defined($call_number);

   print NEWFILE "<match>\n";
   print NEWFILE "<title>";
   print NEWFILE $title, "</title>\n";
   print NEWFILE "<isbn>";
   print NEWFILE $isbn, "</isbnr>\n";  #typo? isbn*r*
   print NEWFILE "<call_number>";
   print NEWFILE $call_number,"</call_number>";
   print NEWFILE "</match>\n";
}