open (FH, $filename) or die ...
local $/ = "\n\n"; # read objects, not lines
while (<FH>) {
  chomp($_); # remove \n\n at the end of the object

  s/\n //g; # care for continuation lines, e.g. kill them
  my @tmpLines = split(/\n\n/, $_);
  my %data = ();

  foreach my $line (@tmpLines) {
    my ($attr, $value) = split(/\s*=\s*/, $line, 2);

    # do something with $attr and $value, e.g.
    push (@{ $data{$attr} }, $value);

  } # foreach

  # e.g. extract first uid as dn
  my $dn = shift( @{ $data{uid} } );

  print "dn: $dn\n";
  foreach my $attr (keys %data) {
    foreach my $value (@{ $data{$key} }) {

      # perhaps you should care to create continuation lines
      # or better write the ldif with Net::LDAP::LDIF
      print "$attr: $value\n";     
    }
  }
  print "\n"; # object separator

} # while
close (FH);
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