The code you posted is broken and I am no Mojolicious user (yet), but...

if you meant

    
get '/' => sub {
  my $c = shift;
  $c->render;
} => 'index';
[download]

then it's the same as

    
get ('/' , sub { ... } , 'index');
[download]

( sub body shortened for clarity )

In other words, you are calling get with three parameters.

Please look up "fat comma", i.e. => is just a , with stringification of the left hand side.

In this case the => is just syntactic sugar, b/c no stringification happening here, but it reads better.