use strict;
use warnings;
use Data::Dumper;

my $result = {};
local $/ = "\n\n";
while(my $block = <DATA> ){
    chomp $block;
    my %info = map{
        split /\s*:\s*/, $_, 2
    }split /\n/, $block;
   
    my $oid = $info{SamAccountName};
    $result->{$oid} = \%info;
}
print Dumper $result;


__DATA__
SamAccountName  : U011004
LastLogonDate   : 20.06.2016 15:01:10
ExpiryDate      : 19.12.2016 13:58:05
PasswordLastSet : 20.06.2016 14:58:05
mail            : J.W@dbx.com

SamAccountName  : U011001
LastLogonDate   : 25.05.2016 09:53:51
ExpiryDate      : 23.11.2016 08:53:28
PasswordLastSet : 25.05.2016 09:53:28
mail            : MM.AA@yxz.de