What the @ Means

Two lessons in a row used tags starting with @ — <@placeholder>, <@catch|err|> — without explaining the prefix. Before this part closes, let’s name it, because it’s not try-specific syntax. It’s a glimpse of Marko’s most distinctive feature.

An @-tag is an attribute tag: a named piece of content passed to the tag it sits inside. Regular tag content answers “what goes in the body?” — attribute tags answer “what goes in each named slot?” <try> declares two slots, placeholder and catch, and you fill them:

<try>
  ...the body...

  <@placeholder> ...pending slot... </@placeholder>
  <@catch|err|> ...error slot, receiving the error... </@catch>
</try>

Notice everything you already know composes here: an attribute tag has content like a tag, and parameters like a loop — |err| is the same pipes from <for> and <await>.

What makes this Marko’s signature: your own tags can declare slots too — a card with @header and @footer, a table with a @cell per column, repeated and conditional slots. That’s part four’s opening act; this lesson just hands you the vocabulary.

Quick hands-on to seal it: the <try> on the right handles errors but streams in-order — its slow await has no placeholder.

1. Add the missing slot: <@placeholder><p>Warming up…</p></@placeholder> inside the <try>, sibling to the <@catch>.
2. Reload the preview: placeholder first, content replaces it — and you can now read every character of that markup precisely: one tag, a body, and two named, filled slots.