I'm bringing goto back

Yeah, "goto considered harmful" considered harmful.
It's so easy to parse when it's one command per line...

Here's what I did so far


open FILE, "filename.txt" or die $!;

my @lines = <FILE>;
my %labels;

my $ind = 0;

while ($ind < @lines.length){
    my $cmd = @lines[$ind];
    if ($cmd =~ /^\s*(\w+):$/){
        if (!exists($labels{$1})){
            $labels{$1} = $ind;
        }
    }
    $ind++;
}

$ind = 0;

while ($ind < @lines.length){
    my $cmd = @lines[$ind];
    if ($cmd =~ /^\s*goto (\w+);$/){
        if (exists($labels{$1})){
            $ind = $labels{$1};
        }
    } elsif ($cmd =~ /^\s*print \"(.+)\";$/){
        print $1;
    }
    $ind++;
}

example program:

asd:
print "asd";
goto doge;
print "never printed";
doge:
print "aw! aw!";
goto asd;

Lets see how we can replace an ugly goto with an elegant structured programming constructs.

Given an unstructured loop

line1:
  printf("Dijkstra sucks cocks in hell.\n");
  goto line1;


Without sacrificing any expressiveness, we can refactor it using goto into:

line = 0;
while (line++ > 0)
{
  switch(line)
  {
  case 1: printf("Dijkstra sucks cocks in hell.\n") break;
  case 2: line = 1; break;
  }
}


Not only did we killed goto, but also gained a way to address lines of code programmatically. I.e. we can compute the next value of "line" variable.