sub decimalToX {
    my $number = shift or return $_[0];
    my $base = @_;
    my $logbase = log $base;
    my $string = '';

    my $power = int(log($number)/$logbase);

    while($number){

        my $f = $base ** $power;
        my $times = int($number/$f);

        $string .= $_[$times];
        $number -= $times * $f;

    } continue {
        --$power
    }

    $string . $_[0] x ($power+1)
}
print decimaltoX( 5 , qw/0 1/ ); # 101