as ()

The as () (originally tell ()) block is a c-shaped block that runs the script inside in another sprite of its choosing, or the Stage. It can be used as a replacement for the broadcast block.

as ()
Block Type	C-Shape Block
Category / Extension	Control

This was a block lifted from Snap!, another programming language that was originally a modification of Scratch before becoming separate.

Workaround

This block can be worked around by broadcasting a message to another sprite or the Stage with the code wanted:

when I receive [run code v]
code::grey

If clones are used (since clones receive broadcasts), the is clone? block can be used to detect clones.
However, this can cause too many broadcasts to be created when only one sprite needs to run code.