This one-liner draws a patchy pattern using a simple game-of-life-like cellular automaton. You can see the pattern evolving.

If you use a larger terminal window, the pattern is larger as well, but the program gets slower. In general, this program isn't written with speed in mind, it could be made much faster. 

perl -we '($H,$W)=`stty size`=~/^(\d+) (\d+)/?($1-1,$2):(24,80);$w=$W+
+20;@a = map { rand() < 1/3 } 0 .. ($H+20)*$w; print "\e[H\e[J"; for (
+0 .. 30) { print "\e[H"; for (0 .. 1) { @a = map { $c = $_; $s = 0; $
+s += $a[($c + $_) % @a] for -$w-1, -$w, -$w+1, -1, 1, $w-1, $w, $w+1;
+ $s < 3 } 0 .. @a - 1; } for $y (10 .. $H + 9) { for $x (10 .. $W + 9
+) { print $a[$y*$w + $x] ? "#" : " "; } print "\n"; } }'

[download]

Update: you can try changing the parameter 1/3.

In reply to Patchy pattern using a cellular automaton by ambrus

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