My suggestion would be to just run your own http event based sever in perl.

Example this would wait for request to http://localhost/doBigThing, then it sends back text message, then it start doing the big fancy database stuff, before going back to waiting again:

use AnyEvent;
use AnyEvent::HTTPD;
my $httpd = AnyEvent::HTTPD->new (port => 9090);

my $cv = AnyEvent->condvar;
$httpd->reg_cb (
   '/doBigThing' => sub {
      my ($httpd, $req) = @_;
       $req->respond ({ content => ['text/html',"OK starting big datab
+ase thingy now... I will be busy for several minutes.... " ]});
      $cv->send;
   }
);

while (1)
{
    $cv->recv;
    print "Doing big fancy database stuff for a long time here...";
    
    $cv = AnyEvent->condvar;
}
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