[mhalle]

The use of {} for strings without substitutions and effectively for scope are actually interrelated, remarkably.

Scopes are special syntactic forms that delegate variable substitution to the associated procedures. For example, a "for" statement evaluates the body of the function after substituting the loop variable. In a string based language, that's basically the same as expressing the scope in a string form where the string content is passed verbatim as an argument without variable substitution or function invocation.

Having used Tcl extensively back in the day, I am not sure that this syntactic cleverness really was a major impediment to adoption. It was just something to learn. Same was true with [] meaning lisp-like function calling rather than array definition.

Baseline Tcl's biggest challenge, in my opinion, was providing mechanisms to write modular code for larger programs and data encapsulation. Core Tcl put off decisions about the appropriate mechanisms to do so by only providing "namespaces" as a building block for higher level third-party syntax. That led to fragmentation at a time when other languages were gaining popularity.

[jancsika]

> Baseline Tcl's biggest challenge, in my opinion, was providing mechanisms to write modular code for larger programs and data encapsulation.

I don't know if something about tcl's design precluded lexical scoping and a normal "var" keyword. But "upvar" definitely seems like a smell.