When you run this with any argument, for example:

    % perl blocks x
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the program simply displays itself using all '#' characters (which makes it easier to read the letters depicted in the blocks in the ascii picture).

When run without arguments, the output gets REALLY interesting!

Warning -- this program is fairly memory intensive, so it's not recommended that you run it on a system with lots of other processes running concurrently.

Update:  Note, too, that the program creates/overwrites a file called 'x' in the current directory.  (Thanks shmem!)

Update 2:  Also note (especially for Linux users) that the Tk module must be installed.

Update 3:  A hint about deconstructing the program is this -- try running Deparse on the temporary file "x" which is created:  perl -MO=Deparse x

                                                               
if(pop){undef$/;open$x,$0;$_=<$x>;s/\S/#/g;die$_}              
                                                               
                                                               
                           s''                                 
                          useQTk;                              
                         P($M=newQMa                           
                        inWindow);$M->g                        
                       eometry("0x0");subQ                     
                      J{sprintf"#%02x%02x%02                   
                     x",randQ256,randQ256,r a                  
                    ndQ256}subQA{$m->geome tr                  
                      y(sprintf"%dx%d+%d+ %d"                  
                    ,$   s,$s,$x-$s/2,$y -$s/                  
                    2)}su   bQP{$_[0]-> overr                  
                    ideredir   ect(1)} subQH{                  
                    ($G,$H,$I)=   ($_ [0]->ge                  
                    ometr    y=~/(   \d+)\+(.                  
                    +)\+       (.+)/ );($H+$G                  
                    /2,   $I+   $G/2 )}subQ_{                  
                    @C=  (J,J,   J,J )}_;$A=p                  
                    op;     $M-  >af ter(50,                   
                    sub  {m      ap{ ($o,$p                    
                    )=/  4|5/?   (7* $_-27  ,1)                
                   :  (2+((ord)  -54 )/7,  1+((ord             
                  )-54   )%7);$  J.= "#"  x$o.   $"x$          
                 p}split    //,  q[5 77  EUE7      7ER76       
                KL576RTR77E    R76KV 8  7678   :76   =67887    
               697:877;:76=678    87   697:     878@   :RR788  
              REV87:8:RR788REP87;     7:76   6=   788   769F 7 
             87687:766=78876967UEZ:  7677   G876K       77H FM 
            :7677G876K88SKM<78GE96 K   PYKS<77SR87KV86977< 777 
           7847897:86977<7777:699 7: YE   S<SS:HEVSEM<SS: HEP; 
             9G<7777:699J;968<77 778 47896   ;;K77N7777R 87K7: 
           ;K   86N7778E96K86]; ($s, $d)=($A%   2)?(37, -8):(4 
           ,3);w   hile($q=sub str$J ,0,  80,"")   {++ $r;$j=0 
           ;_QifQ$A   >1;map{ $x=30+ 12*  ++$j;$y=1   2*(11+$r 
           +2*  ($r>10   )); if(!/Q/ ){P  ($m=$M->Top level);_ 
           Qif    $A>3;$m   ->config ure    (-hi  ghl ightt=>1 
           ,-hig    hlightb =>"black ",-      bg  =>$ C[($j<31 
           )+2*($     r<11) ]);push@ A,$  m;      &A} }split/  
           /,$q;$   m   ->u pdate}wh ile  (13!    =$s ){$s+=   
           $d  ;@   B=  @A; while(@  B){  $_=spl  ice @B,ra    
           nd   @   B,1,(); ($m,$s     ,$x,$y)=(  $_, $s,H     
           ($_      ));&A;$ _->up         date}}  sle epQ      
             3;ma   p{$b=sp lice             @A,  ran d@       
                A,1,();$b-> wit                 hdraw }        
                   @A;exit} );                     Ma          
                      inLoo p                                  
                         ';s        /\s//gx;                   
                                   s/Q/$"/gx;                  
                                  open$X,">x";                 
                                  print $X $_;                 
                                  map{ system(                 
                                   "perl x $_                  
                                    ")} 0..5
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