It's not a syntactic limitation, it's one of style and convention. The convention seems to be not putting space around the arrow operator. However, there are times where it's appropriate. Have a look at Test::Mojo for an example of where using a little whitespace with the arrow operator turns out to be quite elegant (for some values of elegant).

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 $t->websocket_ok('/echo')
    ->send_ok('hello')
    ->message_ok
    ->message_is('echo: hello')
    ->finish_ok;
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This works because many object methods in the Mojolicious world return a reference to their object instance, so you can chain calls one after the other in that fashion.

About the only other time that I'll add whitespace around a -> operator is when it makes most sense to break a long line there:

my $value = decode_json($json)
    ->{'foo'}[0]{'bar'};
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That's a contrived example, but occasionally putting a line break at the first arrow improves readability.