#!/usr/bin/env perl

use strict;
use warnings;

my %hash = (
    'ScreenName1.Description1' => {
        'ScreenName' => 'A',
        'Description' => 'Desc1',
        'Type' => 'On/Off'
    },
    'ScreenName2.Description2' => {
        'ScreenName' => 'B',
        'Description' => 'Desc2',
        'Type' => 'Momentary'
    },
    'ScreenName3.Description3' => {
        'ScreenName' => 'A',
        'Description' => 'Desc3',
        'Type' => 'Momentary'
    },
    'ScreenName4.Description4' => {
        'ScreenName' => 'A',
        'Description' => 'Desc4',
        'Type' => 'On/Off'
    },
    'ScreenName5.Description5' => {
        'ScreenName' => 'B',
        'Description' => 'Desc5',
        'Type' => 'On/Off'
    },
);

my %parsed;

for (values %hash) {
    push @{$parsed{$_->{ScreenName}}},
        join ' ', @{$_}{qw{Description Type}};
}

print "*** Counts ***\n";
print "$_ - ", 0+@{$parsed{$_}}, "\n" for keys %parsed;
print "\n*** New hash (\%parsed) ***\n";
use Data::Dump;
dd \%parsed;

##</code><code>##

*** Counts ***
A - 3
B - 2

*** New hash (%parsed) ***
{
  A => ["Desc1 On/Off", "Desc3 Momentary", "Desc4 On/Off"],
  B => ["Desc2 Momentary", "Desc5 On/Off"],
}

##</code><code>##

*** Counts ***
B - 2
A - 3

*** New hash (%parsed) ***
{
  A => ["Desc3 Momentary", "Desc1 On/Off", "Desc4 On/Off"],
  B => ["Desc5 On/Off", "Desc2 Momentary"],
}