use strict;
use warnings;

open FILE1, '<', 'file1.txt' or die ($!);
open FILE2, '<', 'file2.txt' or die ($!);

#- my %file1 = map { split '\|', $_ } <FILE1>;
my %file1 = map { chomp && s/\|$//g && split '\|', $_, 2 } <FILE1>;
#- my %file2 = map { split '\|', $_ } <FILE2>;
my %file2 = map { chomp && s/\|$//g && split '\|', $_, 2 } <FILE2>;
## we now have A1=>'dog' in one hash, and A1=>'Fido' in the other

close FILE1;
close FILE2;

open FILE3, '>', 'file3.txt' or die ($!);
for (sort keys %file1) {
   print FILE3 join('|',$_,$file1{$_},$file2{$_}),'|',"\n";
}
close FILE3;

##</code><code>##

my %file1;
while (<FILE1>) {
  chomp; s/\|[\s]*$//;
  my ($key, $val) = split '\|', $_, 2;
  $file1{$key} = $val;
}