can you elaborate? I always wonder if I should learn it, how it would make me think in new ways and how I would use it. Tcl looks strange and that makes it very interesting for me so how do you use it and why do you use Tcl for it?

It offers the syntactic freedom of Lisp/Scheme without the parentheses.

The top level of parenthesis-es is left out, the other levels replaced by brackets :). But joking aside, I greatly enjoy both Lisp and Tcl as languages.

A huge, seriously annoying problem with TCL is lack of deterministic cleanup for resources. If you don't manually close a filehandle, for example, it will leak. Doing this sort of bookkeeping in 2015 is infuriating.

This illustrates how you can use Tcl to ensure that files get closed even when errors happen by combining catch, close and return (from the Tcl manual):

    proc withOpenFile {filename channelVar script} {
        upvar 1 $channelVar chan
        set chan [open $filename]
        catch {
            uplevel 1 $script
        } result options
        close $chan
        return -options $options $result
    }

  proc with {file as name block} {
    uplevel 1 [list set $name $file]
    uplevel 1 [list eval $block]
    uplevel 1 [list close $file]
  }
  
  with [open foo.txt w] as file {
    puts $file "Hello, World!"
  }

I'm sure it's possible to do it in a cleaner way without [set], but my Tcl is a bit rusty.

I like the "with". Python has that construct. It's not annoying and easy to remember.

Still leaks on an exception. That's also an annoying construct to be forced to use.

You could easily wrap the middle uplevel in a catch block to handle exceptions, and this sort of "with" construct is pretty common in a lot of very popular languages today.

While it would be nice if this were baked into the language, it's pretty astonishing how extensible Tcl is without even having to touch the realm of C extensions.

I think this precisely one of Tcl's strengths. Few other languages apart from Lisp and Tcl lets you write your own control flow syntax from within the language (and at runtime).

Garbage collecting languages will free memory, but that's all they're good for. C++ destructors will let you close a filehandle, but I know of no other language that will deterministically clean up non-memory resources.

So: What language(s) did you have in mind that do this right?

Lisp for example has unwind-protect, which is guaranteed to run the unwind code when you leave its scope in which way whatever (be it an exception or a return). So this is a reliable way of running clean-up code at the end of a code block.

Many scripting languages in practice do reference counting GC that will reliably and deterministically clean up resources other than memory.

"Many" includes Tcl there. I have no idea why you think differently. Tcl has had it since the 8.X series started (at least).

Not for tcloo objects, channels and file handles. I don't think you get it. In sane languages like C++ you can expect a destructor to call itself no matter where a function exited.

C++ is not a scripting language. Give me a scripting language that does that so I can research and compare.

perl:

    sub do_stuff {
        my $thing = Thing->new; # no need to manually destroy thing. Its DESTROY method will be called at the closing brace.
    }

Cool...now I get to play. Perl does it because it goes out of scope once the sub is run. I am pretty sure you can tell TclOO to do the same thing (play time) if it already doesn't do that.

In the end, they all make trade offs depending on the "whim" of the language designer.

Jesus Christ, you don't even know tcl. Why are you blathering on here? No, tcloo objects are not garbage collected. That's the whole point here.

Yeah just blathering. Carry on.

So, about four posts before this one, you said:

> Many scripting languages in practice do reference counting GC that will reliably and deterministically clean up resources other than memory.

When challenged, you offered one. So, is this a Perl-only thing, or can you give other examples?

Programming must by hard for you. Have a cookie.

I do a lot of text mining and it's one of the most efficient languages I've used over the years for doing things like this.

That's an unusual assertion. Perl has much better facilities for working with unicode, and many other advanced facilities for parsing and so forth.

> Perl has much better facilities for working with unicode

Which facilities are those ?

> many other advanced facilities for parsing

Be curious to hear what those are, but note that Tcl is hilariously simple to extend and build up custom constructs to suit ones needs.

Not to mention that Tcl has Unicode in the core, has had Unicode in the core for at least 8 years, and the long and short is that EVERY string operation is Unicode aware.

You can have unicode procedure names, if that was your fancy.

...right, which is why I was wondering where Perl's support is superior. Tcl's support isn't perfect nor complete, but it's still pretty impressive.

I would like to see what advanced facilities perl has for text parsing that TCL doesn't!

Me too, but I suspect it might take someone of tchrist's level with experience in both languages to give a good answer. I would be interested in how TCL handles the issues tchirst has to deal with outlined in his famous SO post[1].

Note: If you read that post and think, "Wow, Perl requires a lot of setup for unicode and TCP doesn't require nearly as much" without understanding the specifics of why each step is there, and how TCL handles the same issue, you are likely underthinking the issue.

1: http://stackoverflow.com/questions/6162484/why-does-modern-p...

TCL/TK is incredibly powerful to put a GUI in front of a bunch of scripts. You can easily bind a regexp in a log file to events that update widgets. I wish I had learned it 20 years ago.

Could you give an example of that?

If by "that" you mean an example of a GUI on top of scripts, the `git gui` and `gitk` that ship with git are in Tcl/Tk and shell out to the git commands that do the work

As others have mentioned, they are very, very not "native UI" friendly - OSX is an especially bad instance - but they do run on all of Git's platforms without a 20MB runtime to go along with them. If Tk's widgets were just a little less harsh, those two would absolutely be my go-to graphical git clients.

We use TCL for almost everything that isn't C/C++, its insanely flexible. You can completely redefine the syntax if you want as there are NO keywords. Meta programming is easy, as all TCL commands follow the same format- Its only con is the lack of widespread use, so sometimes you'll have to write your own packages.

Dont worry to much though, the syntax grows on you :)

This is a great introduction, by antirez of redis-fame.

http://antirez.com/articoli/tclmisunderstood.html

Tcl is also the de-facto default language for almost all VLSI tools

This post occasionally makes the rounds and is an enlightening read:

http://antirez.com/articoli/tclmisunderstood.html

Yup, I whip up little one off utilities all the time with Tcl/Tk.