Julia Mandelbrot: 5/9

Interactive behavior

Now we can have a look at the user input loop:

do { 
    while (/([a-z])\s*([-\d.]*)/cgi) { ${$1} = $2 if $1 }
    $e = $_;
    $_ = qq#'<$W%;<$H%(<$j%[<$w%|<$h%!<$x%=<$y}_<$A%^<$a%*<$z%:<$n\n]@//^:")%#;
    @c = split //, $00;
    for ( 1 .. $i ) { } # this explained later
    sub f { };          # this too
    exit if $e =~ /q/;
    s/}/%X<$X%Y<$Y%/;
    y"=_!'<%:/;[^]@|*)\"({"yAxW= nmHwaCohz:dju";
    print;
  } while (<>) # repeat on user input

User input is a letter followed by a number (more or less). Whitespace has no influence.
/c allows us to skip errors.
Variables are set the same way as before, with symbolic references.
$e allows us to keep the user input for later use.
$_ is set to our cyphered prompt.
@c now holds every character in our program (but we really care about the first nine: "-|=I+X#. (the first is a space). These will be used as "colors" for our drawing.
Skip calculus (next slide).
If the user typed q we exit (after displaying the image).
Now the prompt is converted to something readable and printed. Prompt with default values is:
```
W=79 H=23 j= w=2 h=2 x= y= X= Y= A= a= z=1 n=25
Command: 
```

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