This is a simple sudoku solver (if written unformatted, it's about 7x80-char lines of code). I'm a beginner in Perl, and this looked like a good first program, but of course there are surely many naiveties in the code. Any criticism/remark/comments welcome.

               use strict;
           use warnings;my @r;
        sub r{my $l=shift;my%x=();
      for(0..8){$x{int($l/9)*9+$_}=""
    ;$x{($l%9)+($_*9)}="";}my$k=int($l
    /27)*27+int(          ($l%9)/3)*3;
    @x{$k..$k+2,          $k+9..$k+11,
     $k+18..$k+20           }=("")x9; 
      delete $x{$l};
        return %x;}sub
          v{for(0..80){
            next if($_[$_
              ]eq".");return
                0 if (join("",
                  @_[@{$r[$_]}])
                    =~/$_[$_]/) }
                      return 1}sub z{
    my($p,@s)=          (shift,@_); v(
   @s)||return 0;         print"Cur: ",
   @s;for(;$s[$p          ]ne".";$p++){
    return print"end: ",@s if($p==81);
     }for(1..9){$s[$p]=$_;return 1 if
       (z($p+1,@s));}}for(0..80){my
        %r=r($_);$r[$_]=[keys %r];
           };z(0,split(//,<>));
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To use it, just give it the 81-chars string representing the board on stdin, eg

echo ".21.3.74.9.8...1 (snip) 3.9.65.1.42." | sudoku.pl
[download]