#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11112008
use warnings;
use List::Util qw( uniq );

my $aref = [
   { 'cname' => 'Smart Parking',     'balance' => 10.12, },
   { 'cname' => 'Smart Parking',     'balance' => 10.22, },
   { 'cname' => 'Smart Parking',     'balance' => 10.32, },
   { 'cname' => 'Highview Parking',  'balance' => 20.12, },
   { 'cname' => 'Highview Parking',  'balance' => 20.22, },
   { 'cname' => 'Highview Parking',  'balance' => 20.32, },
   { 'cname' => 'Highview Parking',  'balance' => 20.42, },
   { 'cname' => 'ParkingEye',        'balance' => 30.12, },
   { 'cname' => 'ParkingEye',        'balance' => 30.22, },
   ];

my %temphash;

for ( @$aref )
  {
  $temphash{$_->{cname}}{cname} = $_->{cname};
  $temphash{$_->{cname}}{balance} += $_->{balance};
  $temphash{$_->{cname}}{total}++;
  }

my $answer = [ @temphash{ uniq map $_->{cname}, @$aref } ];

use Data::Dump 'dd'; dd $answer;