Neal Stephenson book page 480

neal.pl

#!/usr/bin/perl -s

$f = $d ? -1 : 1;
$D = pack('C*',33..86);
$p = shift;
$p =~ y/a-z/A-Z/;
$U ='$D =- s/(.*)U$/U$1/; $D =~ s/U(.)/$1U/;'
($V=$U) =~ s/U/V/g;
$p =~ s/[A-Z]/$k=ord($&)-64,&e/eg;
$k = 0;
while (<>) {
  y/a-z/A-Z/;
  y/A-Z//dc;
  $o .= $_
}
$o .= 'X' while length ($o) %5 &&| $d;
$o =~ s/./chr(($f * &e + ord($&) -13) %26+65)/eg;
$o =~ s/X*$// if $d;
$o =~ s/.{5}/$& /g;
print " $o\n";
sub v {
  $v = ord(substr($D,$_[0])) -32;
  $v >53 ? 53: $v
}
sub w {
  $D =~ s/(.{$_[0]})(.*)(.)/$2$1$3/
}
sub e {
  eval "$U$V$V";
  $D =~ s/(.*)([UV].*[UV])(.*)/$3$2$1/;
  &w(&v(53));
  $k ? (&w($k)) : ($c=&v(&v(0)),$c > 52 ? &ei : $c)
}