Note that you can swap without temp variables:

    for( 0 .. $#$ref ) {
        my $p = $_ + rand( $n-- );
        @{$ref}[$p,$_] = @{$ref}[$_,$p];
    }
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sub my_shuffle2 {
    my $ref = \@_;
use List::Util 'shuffle';
    @{$ref}[0..$#$ref] = shuffle(@$ref);
    return unless defined wantarray;
    return wantarray ? @{ $ref } : $ref;
}
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