In a way, it's nice when no one else gets to one of these. It gives my slow wits a chance to do something in my scattered spare time:

sub x{
  ($l,$t,$c,$n)=@_;                                     #  17

  while($_=chop$n){                                     #  17

    $b=\substr$t,index($l,chop$c),1;                    #  32

    /$$b/||$$b=~/ /&&$t!~/$_/||return;                  #  34

    $$b=$_                                              #   6
  }                                                     #   1
  $t                                                    #   2
}
                                                        # 109 chars

$alpha="abcdeflprxyz";
$trans="            ";

$cipher="abcadbbe";
$word="deadbeef";
$trans = x($alpha,$trans,$cipher,$word);
$_=$cipher;
$trans and eval"tr/$alpha/$trans/";
print;

$cipher="zbxf";
$word="perl";
$trans = x($alpha,$trans,$cipher,$word);
$_=$cipher;
$trans and eval"tr/$alpha/$trans/";
print;
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