my $url="https://stream-fra.watsonplatform.net/speech-to-text/api/v1/recognize";
my $apikey="xxx";
open($fh, "<", "audio-file.flac") or die "Can't read file: $!";
my $audio = do { local $/; <$fh> };
close($fh);

$ua = LWP::UserAgent->new();
 $response = $ua->post(
	$url, 
	apikey => $apikey,
	Content_Type => 'audio/flac',
	Content => $audio
	);