sub perms {
    return !@_ ? [] : map{
        my $next = $_;
        map{
            [ $_[ $next ], @$_ ]
        } perms( @_[ 0 .. $_-1, $_+1 .. $#_ ] );
    } 0 .. $#_;
}

print @$_ for perms qw[ a b c ];;
a b c
a c b
b a c
b c a
c a b
c b a