Well you probably want to read perlreftut but how about this:

my ($location, $h);
while(<DATA>){
    chomp;
    $location = $_ if m/^[a-zA-Z]/;
    next unless m/(\d+)\s+(\d+)/;
    $h->{$location}->{windows}++;
    $h->{$location}->{frames}->{"$1x$2"}++;
    $h->{$location}->{total_length}+= $1*2 + $2*2;
}
use Data::Dumper;
print Dumper $h;

my $fixed_cost_per_window = 100;
my $cost_by_material      = 0.5;
my $total;
for my $location( keys %$h ) {
    my $fixed = $h->{$location}->{windows} * $fixed_cost_per_window;
    my $materials = $h->{$location}->{total_length} * $cost_by_materia
+l;
    printf "%-10s\t%d windows \$%7.2f\tmaterials \$%7.2f\ttotal \$%7.2
+f\n", 
        $location, $h->{$location}->{windows}, $fixed, $materials, $fi
+xed+$materials;
    $total += $fixed+$materials;
}
    printf "\nTotal: \$%.2f\n", $total;

__DATA__
office 1

120 120

120 120

140 135

155 135

120 120

bedroom 2

100 75

100 75

120 180
[download]

This produces:

$VAR1 = {
          'bedroom 2' => {
                           'frames' => {
                                         '120x180' => '1',
                                         '100x75' => '2'
                                       },
                           'windows' => '3',
                           'total_length' => '1300'
                         },
          'office 1' => {
                          'frames' => {
                                        '155x135' => '1',
                                        '140x135' => '1',
                                        '120x120' => '3'
                                      },
                          'windows' => '5',
                          'total_length' => '2570'
                        }
        };
bedroom 2     3 windows $ 300.00    materials $ 650.00    total $ 950.
+00
office 1      5 windows $ 500.00    materials $1285.00    total $1785.
+00

Total: $2735.00
[download]