#! perl -w
my %data;
open IN, "file1.txt" or die "Ugh! $!";
while(<IN>) {
    chomp;
    my($key, $value) = split /\|/ or next;
    $data{$key}[0] = $value;
}

open IN, "file2.txt" or die "Ugh! $!";
while(<IN>) {
    chomp;
    my($key, $value) = split /\|/ or next;
    $data{$key}[1] = $value;
}

{
    open OUT, ">file3.txt" or die "Ugh! $!";
    local($\, $,) = ("|\n", "|");
    local $^W;  # avoid "use of uninitialized value"
    foreach (sort keys %data) {
        print OUT $_, @{$data{$_}}[0, 1];
    }
}