One information which I forgot to add is that @{[...]} is a construct to tunnel Perl code into string interpolation.

This is handy if you don't have a template engine.

For instance

my $tmpl = << "__HTML__";

... some HTML ...

<h1>@{[
  text (
      en => "title",
      de => "Titel",
  )
]}</h1>

... more HTML ...

__HTML__
[download]

is code I actively use in a CGI where the sub text() decides which language to insert.

The code is executed in list context, that's why %hash get expanded to a list.

HTH!