Why a colon at the end of a block statement?

[perklet]

from the official site:

<% if @links?.length : %>
    <ul>
        <% for link in @links : %>
            <%- linkHelper link %>
        <% end %>
    </ul>
<% else : %>
    <p>List is empty</p>
<% end %>

What is the purpose of using a colon at the end? It's not a CoffeeScript syntax.
And will it be removed in the future?

[baryshev]

CoffeeScript uses indentation to denote code blocks. We can't use indentation for this purpose inside of templates, because templates have it's own indentation in HTML. Colon and end statements is not a part of CoffeeScript, it's a part of ECT. Also ECT uses this syntax to be fully compatible with ECO, because ECT is positioned as fast and more powerful ECO alternative.