use Time::HiRes qw( sleep gettimeofday tv_interval );
# ...
sub main {
    state $db_handle = mock_connect(+shift);
    sub {
        my $t0 = [ gettimeofday ];
        [ 200, [],
          [ sprintf "Application sub took %.6f seconds\n",
                tv_interval( $t0, [ gettimeofday ] ) ] ];
    };
}
# ...
__END__
moo@cow[56]~>curl http://0:5000/
Application sub took 0.000001 seconds
moo@cow[57]~>curl http://0:5000/
Application sub took 0.000002 seconds