async sub fetch {
my $loop = IO::Async::Loop->new;
my @data;
my $client = Net::Async::WebSocket::Client->new(
  on_text_frame => sub {
    my ( $clientself, $frame ) = @_;
    ...
    push @data, $frame;
    # when I had enough frames
    if( 10 < scalar @data ){
      say "I am ".__PACKAGE__."::fetch() and we had enough data";
      $clientself->close; $loop->stop;
      return;
    }
  } # on_text_frame
);
$loop->add( $client );
await $client->connect(url => $myurl);
# tell the WS that we need data
$client->send_text_frame('send me data');
$loop->run;
my $retdata = Future->done(\@data)->get;
# save $retdata to file
...
# and return
return $retdata;
}
sub give_me_data {
  # collapse the future
  my $data = $self->fetch()->get();
  # process data
  ...
  return $processed_data
}

##</code><code>##

# main
use ModuleA;
use ModuleB;

sub give_me_data {
   # no Future here:
   my $dataA = ModuleA->new()->give_me_data();
   my $dataB = ModuleB->new()->give_me_data();
   return ...
}