#!/usr/bin/perl
use strict;
use warnings;

open( my $fh, '<', "ldif.file") or die $!;
$/="";
while( my $item=<$fh> ){

    print "===========\n";
    print "$item\n";
    print "===========\n";

    if ($item =~ /something/is ){
        print "as you like\n";
    }
}
close $fh;

__DATA__
===========
dn: uid=testing,ou=comp,o=test.com
dpwnc: BH
mail: example@great.com
sn: example


===========
===========
dn: uid=testing1,ou=comp,o=test.com
dpwnc: CH
mail: example1@great.com
sn: example1


===========
===========
dn: uid=testing2,ou=comp,o=test.com
dpwnc: DH
mail: example2@great.com
sn: example2

===========