my %lookup; 
while (<$LDIF>) {
   my ($dn)    = /^dn: (.*)$/m;
   my ($samACCOUNTNAME) = /^samACCOUNTNAME: (.*)$/m;
   $lookup{$dn} = $samACCOUNTNAME
    if defined $dn and defined $samACCOUNTNAME; # only if both are found
}