my @sortrecs = map { $_->[0] }
               sort { $a->[1] <=> $b->[1] }
               map { [ $_, 
                 ( split /=\s*/, (grep { /area/ } @{$_} ) )[1] ] }
               @records;

##</code><code>##

use strict;
use warnings;
my @records;
{
    local $/ = "\n\n";
    open IN, "<", "infile.dat" or die "Bleah\n$!";
    while ( my $record = <IN> ) {
        my %rechash;
        foreach my $kvpair ( split /\n/, $record ) {
            my ( $key, $val ) = split /\s*=\s*/, $kvpair;
            $rechash{$key} = $val;
        }
        push @records, { %rechash };
    }
    close FH;
}
my @sortrecs = sort { $a->{'area'} <=> $b->{'area'} }
               @records;

open OUT, ">", "outfile.dat" or die "Ick!\n$!";
foreach my $record ( @sortrecs ) {
    while ( my ( $key, $val ) = each %{$record} ) {
        print OUT "$key = $val\n";
    }
    print "\n";
}
close OUT or die "Argh!\n$!";