Implement Bogosort

Perl 6: 23 chars

@s.=pick(*)until[<=] @s

APL(Dyalog), 20

{⍵≡⍵[⍋⍵]:⍵⋄∇⍵[?⍨⍴⍵]}

Explanation

⍵ is the (right) argument
⍵≡⍵[⍋⍵]: Checks if ⍵ sorted equals ⍵ itself
:⍵: If yes, then return ⍵
∇⍵[?⍨⍴⍵]: Else, generate an array of 1 to ⍴⍵ (length of ⍵) in random order, reorder ⍵ according to that (⍵[...]), and apply the function to it (∇)

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Suddenly revisiting this problem and...

APL(Dyalog), 19

{∧/2≤/⍵:⍵⋄∇⍵[?⍨⍴⍵]}

Was just thinking about sorting an array in the check makes it kind of pointless (not saying that Bogosort is meaningful), a more accurate implementation would be ∧/2≤/⍵, and that happens to lower the char count.

Ruby - 33 characters

g=->l{l.shuffle!!=l.sort ?redo:l}