#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
my $hash;
my %results;
for my $row( split("\n",join('',<DATA>)) ){
    my($key1,$key2,$val) = split('\|_\|',$row);
    next if $results{$val} and $hash->{$key1}->{$key2};
    $hash->{$key1}->{$key2}=$val;
    $results{$val}=1;
}
print Dumper $hash;
__DATA__
200326951|_|rel_Access1|_|200315482|_|
200326951|_|rel_Access1|_|200315786|_|
200326951|_|rel_Access2|_|200315482|_|
200326951|_|rel_Access2|_|200315786|_|