$iscurchan(<channel name>)

This function returns '1' if the input channel name is the current channel on any window connected to the current server.

This function was intended to allow more flexibility for testing the current channel in an ON hook.

'1' if <channel name> is a current channel, else returns '0'

Instead of:

   /on ^send_public * {if ([$0] == C) {...} {...}}

Try doing:

   /on ^send_public * {if (iscurchan($0)) {....} {...}}