The documentation states:

Quote
For more flexibility, you can also use Variables in place of both the matchtext and the channel parameters.

on 1:TEXT:%matchtext:%channel:/msg $nick You just said $1- on channel %channel

The value of %matchtext will be matched against whatever text the user sends, and the value of %channel will be matched against the channel to which the message was sent.

Although not explicitly stated, I imagine that the variables mentioned are global variables (the one in the ‘Variables’ tab).

However, the script I'm writing I have variables with dynamic names, like this:

Code
set %prefix_ $+ $chan my Value

Is it possible to create a event trigger like this?

Code
on *:TEXT:%prefix_ [ $+ [ $chan ] ]:#: { ... }