Perl Weekly Challenge 99: overlapping searches

One way to let me improve my knowledge about Raku (aka Perl 6) is to implement programs in it. Unluckily, I don’t have any production code to implement in Raku yet (sob!). So, why not try solving the Perl Weekly Challenge tasks?

In the following, the assigned tasks for Challenge 99.

• Task 1
• Task 2

My eyes…

My last check revealed that there could be a hope, but I have to wait one year since the surgery to let the eye to stabilize. After that period, something could be tried.
Better than nothing!

PWC 99 - Task 1

The first task required to write a program that accepts a shell-like string pattern, where * means any char and ? means a single character.
I’ve decided to convert the input pattern into a regular expression, with appropriate anchors, and then let Raku do the heavy work for me:

sub MAIN( Str $S, Str $P ) {
    # substitute every ? to match a single char
    # and every * to match a stream of chars
    # and add anchors
    my $regexp = '^' ~ $P.subst( '*', '.*' ).subst( '?', '.' ) ~ '$';
    { say 1; exit; } if $S ~~ / <$regexp> /;
    say 0;
}

The idea is that a pattern like a*b?c is translated into the regular expression ^a.*b.c$, so that the matchin engine can work.

PWC 99 - Task 2

The second task is more complex to me, and I was unable to fully complete it. The task required to search for all unique substrings that can be found into another string by composing single characters.
After a lot of work with arrays, I decide to use :exhausistive option of regular expression, that finds me almost all the required substring matches, but not the right solution:_

sub MAIN( Str $S, Str $T ) {
    my $counter = 0;
    my $regexp = $T.comb.join( '.*' );

    # overlapping search
    given $S {
        for m:exhaustive/ <$regexp> / -> $match {
            $counter++;
        }
    }

    say $counter;
}

I do compile the string placing a .* between every character, and asking the matching engine to work for me. *Again, this is not a completely working solution, but I cannot come up with a better solution right now.