#!/usr/bin/perl
use warnings;
use strict;

my $str = shift;
my $key = join q(), map chr rand 255, 0 .. 255;

print "$key\n";
my $encrypted = $str ^ substr($key,0,length($str));
print "$encrypted\n";
[download]

#include<stdio.h>

int main () {
  char key[255], string[255];
  gets(key);
  gets(string);
  for (int i=0;string[i] != 0;i++) {
    printf("%c", key[i] ^ string[i]);
  }
  return 0;
}
[download]

The ^ operator doesn't seem to work for strings, so I had to iterate the strings character by character.

It seems to work sometimes , I'm not sure why not always. Maybe you can get 0 as a result of the xor somewhere in the middle of a string? Or a newline in the middle of the key? But it should get you started.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]