CR *FDA, 1997, GUID IND EXT REL OR
   BADAWY SIF, 1996, INT J PHARM, V128, P45
   (more lines w. similar formatting)
NR 42
##</code><code>##

use strict;
use warnings;
my @infile = (<>);
my ($citedreferences, $line);
my $n = 0;
foreach $line (@infile){
	if ($line =~ m{^CR .+}gsi){
		do{
		$n++;
		print $n . $line;
		next;
		}
	 until ($line =~ m{^NR}gsi)
}
};