You can use a hash of hashes like this:

use strict;

my %house;
my $room;
while (<DATA>) {
    chomp;
    next unless $_; # skip blank lines

    if(/^\D/) { $room = $_ }
    else      { $house{$room}{$_}++ }
}

foreach my $room (keys %house) {
    print "$room:\n";
    print "width height quantity\n";
    map  { print "$_ $house{$room}{$_}\n"; }
      sort { $house{$room}{$b} <=> $house{$room}{$a} } 
      keys %{$house{$room}};
}

__DATA__
office 1

120 120

120 120

140 135

155 135

120 120

bedroom 2

100 75

100 75

120 180
[download]

Outout:

bedroom 2:
width height quantity
100 75 2
120 180 1
office 1:
width height quantity
120 120 3
140 135 1
155 135 1
[download]