Just tried out the handling with variables and messages and copied the help example into a blank project.

When i rearrange the order "1 two 3" of the help example on the right side I get this error message.
Everytime when there isn't a number on the first place in the message box, I get this error message.

@Bangflip Sort of...... but we are not allowed to call it that.
Messages that start with a float (number) and have more items than one are automatically treated as lists.
But if the first item is text then it is dropped by a [$1 $2 etc.( message, and that puts your $3 out of range.
You can fix that by setting the message explicitly as a list.....
[list two 1 3( will work.

When a message starts with a "text" that text is treated as a selector for routing the rest of the list.
But list is also a selector..... it gets complicated.

We cannot call it a bug because the selector processing is so fundamental to almost every patch ever made that it cannot be changed...... patches made prior to such a massive change would be broken.
There is a thread about it here....... https://forum.pdpatchrepo.info/topic/13636/route-asymbol-doesn-t-match-tagged-symbols
The thread includes some example patches.

"list" has issues too though.
And things get worse when using [route] and [select].
........... pd-selector.pd

Also, if you are (might be?) unsure about global and local variables in Pd ($ dollars) then read this...... https://forum.pdpatchrepo.info/topic/9774/pure-data-noob/4
And make sure you understand the order of operations........ https://forum.pdpatchrepo.info/topic/13320/welcome-to-the-forum
David.

Hey, thank you for the very detailed answer! I appreciate that and learned something again.

I will read me through the links.

@Bangflip to add to what david said, any time there are multiple atoms (things) in a message and the 1st one is a number, the message will get an implicit "list" selector added to the beginning. this is not true of multiple-atom messages that start with a non-number

And this one, which catches me out every time.

hjh