gistfile1.txt

use v6;

my %dictionary;
slurp("big.txt").comb(/<alpha>+/).map({%dictionary{$_.lc}++});

my @alphabet = 'a'..'z';

sub edits($word) {
    my @s = (^$word.chars).map({$word.substr(0, $_), $word.substr($_)});
    my @deletes = @s.map(-> $a, $b { $a ~ $b.substr(1); });
    my @transposes = @s.map(-> $a, $b { $a ~ $b.substr(0, 2).flip ~ $b.substr(2) if $b.chars > 1 });
    my @replaces = @s.map(-> $a, $b { @alphabet.map({$a ~ $_ ~ $b.substr(1)}) });
    my @inserts = (@s,$word,"").map(-> $a, $b { @alphabet.map({$a ~ $_ ~ $b})});
    return (@deletes, @transposes, @replaces, @inserts);
}

sub correct($word) {
    return $word if (%dictionary{$word});
    my @candidates = edits($word).grep({ %dictionary{$_} });
    # @candidates = edits($word).map({ edits($_) }).grep({ %dictionary{$_} }) if @candidates.elems == 0;
    return $word if @candidates.elems == 0;
    return @candidates.max({%dictionary{$_} // 0});
}

correct("lary").say;