Python:

    a = print
    a("Hello World")

Rust:

    fn puts(s: &str) {
        println!("{}", s);
    }
    
    let a = puts;
    a("Hello World");

C++:

    #include <cstdio>

    auto a = puts;
    a("Hello World");

Also: every FP language ever. How is that a fundamental thing about TCL?

Also probably all shell scripting languages, like Bash:

    a=echo
    $a Hello World