# Special Argument
$mime_type = $producer->foo(undef, @args);
$producer->foo($fh, @args);

# Explicit Context
# wantarray is false versus wantarray is undefined
# When wantarray is false we return an object with a
# mime_type method.
$mime_type = $producer->foo(@args)->mime_type;
$producer->foo(@args);

# Implicit Context
# wantarray is false versus wantarray is undefined
# When wantarray is false we return the MIME-Type directly.
$mime_type = $producer->foo(@args);
$producer->foo(@args);

# Callback
# This would have to be augmented with the use of threads
# to really work
my $mime_type;
$producer->foo(sub { $mime_type = $_[0] }, @args);

# Special method
$mime_type = $producer->foo_mime_type(@args);
$producer->foo(@args);

# Double-call (very bad idea, but it's a brainstorm)
select $null_fh;
$mime_type = $producer->foo(@args);
select $real_fh;
$producer->foo(@args);

# Documents as objects
$document = $producer->foo(@args);
$mime_type = $document->mime_type;
$document->render;