How to make translations with parameters work?

[ppazos]

In the doc, there is this example:

echo L::last_modified("today");

That seems to output a text with the "today" replaced using some kind of variable name, but in the sample lang files, an example for that is missing.

What's the format of the lang files to support parameters?

[Philipp15b]

The string is formatted with PHP's vsprintf. I am happy to accept a pull request to add the missing example string.