#!/usr/bin/perl #use strict; open(FILE1,"C:/Perl/BX/BX-Users.txt"); open(FILE2,"C:/Perl/BX/BX-Book-Ratings.txt"); open(result1,">C:/perl/BX/BX-Users_result.txt"); my $i=0; my $j=0; while((my $bxUser=<FILE1>)&&($i<10)) {     my $userId=substr($bxUser,0,index($bxUser,","));     while(my $rankUser=<FILE2>)     {         my $userIdCmp=substr($rankUser,0,index($rankUser,","));         if(($userId==$userIdCmp)&&($j==0))         {             syswrite(result1,"$bxUser");             $j++;         }     }     $j=0;     $i++;     } close(FILE1); close(FILE2); close(result1);