example.ldif

telephoneNumber: 4045554400
mobile: 2145555000
reversedPhone:0005555412
reversedPhone:0044555404
title: Operations Engineer
cn: Smith, John

telephoneNumber: 6785554400
mobile: 3015555000
reversedPhone:0005555103
reversedPhone:0044555876
title: Operations Engineer
cn: Doe, John

example.output

cat example.ldif | ./fix.pl
cn: Smith, John^title: Operations Engineer^phone: 4045554400^phone: 2145555000^mobile: 2145555000^telephoneNumber: 4045554400^
cn: Doe, John^title: Operations Engineer^phone: 6785554400^phone: 3015555000^mobile: 3015555000^telephoneNumber: 6785554400^

fix.pl

#!/usr/bin/env perl

use warnings;
use strict;
use Modern::Perl;

my $count = 0;
my @people;
my $blank = 0;

while (<STDIN>) {
  chomp;
  my $line = $_;
  if ($line =~ m/reversedPhone:/) {
      $blank = 0;
      my @reversed = split ":", $line;
      my $phone = reverse scalar $reversed[1];
      #say "phone: $phone^";
      push @{$people[$count]}, "phone: $phone";
  } elsif ($line eq "") {
      if ( $blank == 0) {
          $count++;
          $blank = 1;
      } else {
          next;
      }
  } else {
      $blank = 0;
      #say "$line^";
      push @{$people[$count]}, "$line";
  }
}

for my $line (@people) {
    my @person = reverse @{$line};
    say map {$_ . "^"} @person;
}