Bisect string weirdness

weird.pl

use v6;
my $str = slurp 'gistfile1.txt';

sub test(Str $str) {
    return not try { $str.perl; True };
}

my $left  = 0;
my $right = $str.chars;

loop {
    say "left: $left;   right: $right;   test: ", test($str.substr($left, $right - $left));
    my $middle = ($right + $left) div 2;
    if test($str.substr($left, $middle - $left)) {
        $right = $middle;
    }
    elsif test($str.substr($middle, $right - $middle)) {
        $left = $middle;
    }
    elsif ($right == $left) {
        say "no result";
        last;
    }
    else {
        my $least = $str.substr($left, $right - $left);
        say "Least remaining string: <<<$least>>>\n";
        say $least.ords;
        last;
    }
};

# vim: ft=perl6