tell
ARES System Manual: tell Utility

tell <key> <channel> <message>: sends a message to the target object or avatar on the specified channel

If <key> is the special keyword 'all', then the message will be sent to every object in the region.

If <key> is NULL_KEY (00000000-0000-0000-0000-000000000000) the message will not be sent.

If <channel> is 'lights', the message will be sent over the system's light bus.

Due to platform restrictions it is not possible to send a message to every object in the region on channel 0.

The message will originate from ring 2 via the io daemon using the io_tell() API call.