Perl merging columns in two text files -

i beginner perl , want merge content of 2 text files. have read similar questions , answers on forum, still cannot resolve issues first file has original id , recoded id of each individual (in first , fourth columns) second file has recoded id , information on of individuals (in first , second columns). want create output file original, recoded , information of these individuals. perl script have created far, not working. if appreciated.

use warnings; use strict; use diagnostics; use vars qw( @fields1 $recoded $original $idf @fields2);  %columns1;  open (file1, "<file1.txt") || die "$!\n couldn't open file1.txt\n"; while ($_ = <file1>) {     chomp;     @fields1=split /\s+/, $_;      $recoded = $fields1[0];     $original = $fields1[3];     %columns1 = (     $recoded => $original     ); };  open (file2, "<file2.txt") || die "$!\n couldnt open file2.txt \n"; ($_ = <file2>) {     chomp;     @fields2=split /\s+/, $_;     $idf= $fields2[0];     $f=$fields2[1];     %columns2 = (     $f => $idf     );   };  close file1; close file2;   open (file3, ">output.txt") ||die "output problem\n";      (keys %columns1) {         if (exists ($columns2{$_}){         print file3 "$_     $columns1{$_}\n"          };     }  close file3; 

one problem scoping. in first loop, have my in front of $column1 makes local loop , not in scope when next loop. %columns1 (which outside of loop) not have values set (which suspect want set). assignment, seem easier have $columns1{$recorded} = $original; assigns value key hash.

in second loop need declare %columns2 outside of loop , possibly use above assignment.

for third loop, in print need add $columns2{$_} in front part of string printed original id printed before recorded id.