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Comment by davidw | Hacker News Reader

Tcl uses blocks for pretty much everything, and they're not that bad looking:

    if { $something } {
        do this
    } else {
        do something else
    }

The first one is actually an expression, but the do this and do something else are simply blocks of code passed to the 'if' command.

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Its beauty (and power) comes with the consistency of the syntax ala Smalltalk / Lisp.

PS. Here's an example of creating something similar with Perl:

    sub IF (&@) {
        my ($block, $flow) = @_;
        [ map { $flow->{$_} || sub {} } qw/else then/ ]->[ $block->() ]->();
    }

    sub THEN (&@) {
        my $block = shift;
        my $flow  = shift || {};
        $flow->{then} = $block;
        $flow;
    }

    sub ELSE (&) {
        my $block = shift;
        +{ else => $block };
    }

    IF { 1 == 0 } THEN { say "True" } ELSE { say "False" };

And with these being functions and not statements we can also do:

    my $result = IF { 1 == 1 } THEN { "True" } ELSE { "False" };

Well, but Tcl blocks are nothing more than strings that you pass as arguments that then get eval'ed using uplevel. Ruby blocks are "real" language constructs, and are real closures, in difference to Tcl blocks.

I can assure you that Tcl blocks are quite "real" in that they are code that gets executed. Initially, yes, they are treated as a string, but then they get byte compiled, and remain 'code' internally.

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