I can actually define this in TCL:

% proc ifn't {cond cmds} {if {!$cond} {uplevel $cmds}}
% ifn't false {puts 12}
12
% ifn't true {puts 12}
% 

I’m struggling to understand if this is true or ifn’t true

I’d take a not or “if not” operator tbh.

Imagine the regex needed to highlight code with that extra single quote.