$ perl -Mstrict -Mwarnings -Mautodie -e '
    my %conf;
    open my $fh, "<", "foo.conf";
    my $data = do { local $/; <$fh> };
    $conf{$1} = $2 while $data =~ /(\w+)="([^"]*)"/g;
    s/\$(\w+)/$conf{$1}/g for values %conf;

    use Data::Dumper;
    print Dumper \%conf;
'
$VAR1 = {
          'A' => 'foo',
          'C' => 'appending foo',
          'B' => 'some other data',
          'D' => '
  some list
  with more data
  and some other data
'
        };