Adding your optimization to BrowerUK's version, we get the best yet.

`sub ikegami (@) {
my @a=@_;
my $i=@a;
my $n;
my $x;
map +( $n=rand($i--), $x=$a[$n], $a[$n]=$a[$i] )[1], @a
}
`

` Rate naive listutil runrig broweruk ikegami
naive 636/s -- -6% -19% -26% -37%
listutil 675/s 6% -- -14% -21% -33%
runrig 785/s 23% 16% -- -9% -22%
broweruk 859/s 35% 27% 9% -- -15%
ikegami 1010/s 59% 50% 29% 18% --
`

Of course, this doesn't always help. For example, try shuffling somewhat long strings.

`our @data = map { 'x' x 1000 } 1..1000;
cmpthese -3, { map { $_ => "$_ \@data" } qw/naive listutil broweruk ru
+nrig ikegami/ };
`

` Rate runrig naive ikegami listutil broweruk
runrig 118/s -- -10% -40% -43% -86%
naive 131/s 11% -- -34% -37% -85%
ikegami 197/s 68% 51% -- -5% -77%
listutil 207/s 76% 58% 5% -- -76%
broweruk 860/s 632% 558% 336% 315% --
`

**Update**: runrig pointed out that my shuffle was broken. I changed `$a[$n]` to `$x=$a[$n]` to fix it. It slowed down my solution, but not by much.

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