Translate custom string from programatically defined block Alright, this one is probably easy but I found online documentation only little helpful and couldn't figure it out myself.

I run a custom module that renders a custom block programatically via function hook_block_view(). Assume that $block['content'] = 'Hello';. The custom string 'Hello' does not appear in the list of translatable strings (config/regional/translate/translate) but I want to display it in, say, Spanish ('Hola') when the site language is set to Spanish.

How do I translate it / make it appear in the list?
In order to make strings translation possible you need to pass it through the t function.

$block['content'] = t('Hello');