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+#!/usr/bin/env perl
+#
+#       The Weekly Challenge - Perl & Raku
+#       (https://theweeklychallenge.org)
+#
+#       Challenge 216 Task 2: Word Stickers
+#
+#       Perl solution by Matthias Muth.
+#
+
+use strict;
+use warnings;
+use feature 'say';
+
+use Data::Dump qw( pp );
+use List::Util qw( min );
+
+sub word_stickers {
+    my ( $stickers, $word ) = @_;
+    say "word_stickers( ", pp( $stickers, $word ), " )";
+
+    # Keep count of how many of each letter we need.
+    my %needed;
+    $needed{$_}++
+        for $word =~ /./g;
+
+    # For any letter, mark which stickers give that letter.
+    # If we need a certain letter, we then can check whether
+    # - the letter is still available from a sticker we already took
+    #   (marked in %available, see further below),
+    # - get one of the stickers that give us that letter
+    #   (marked in @{$letter_stickers{<letter>}}).
+    my %letter_stickers;
+    for my $sticker ( @$stickers ) {
+        # Make sure we add the sticker only once, even if the same letter
+        # occurs several times on the sticker.
+        my %sticker_letters = map { ( $_ => 1 ) } $sticker =~ /./g;
+        push @{$letter_stickers{$_}}, $sticker
+            for keys %sticker_letters;
+    }
+    say "letter stickers:\n", pp( \%letter_stickers );
+    say "needed letters:\n", pp( \%needed );
+
+    # Keep count of how many of each letter we have available from stickers.
+    my %available;
+    my $n_stickers_used = 0;
+    while ( %needed ) {
+        my $resolved_a_letter = 0;
+        for my $letter ( sort keys %needed ) {
+            say "trying to resolve letter '$letter'";
+            # Get stickers if needed.
+            if ( ( $available{$letter} || 0 ) < $needed{$letter} ) {
+                # Get stickers for this letter if there is only one sticker type
+                # that gives us this letter. If not , we wait with this letter.
+                unless ( $letter_stickers{$letter} ) {
+                    say "no sticker for letter '$letter'";
+                    return 0;
+                }
+                if ( @{ $letter_stickers{$letter} // [] } == 1 ) {
+                    my $sticker = $letter_stickers{$letter}[0];
+                    # Get as many stickers of this type as we need for this
+                    # letter, adding all sticker letters to the available
+                    # letters.
+                    # Note that the same letter can appear several times on the
+                    # sticker, so add stickers one by one.
+                    do {
+                        say "adding sticker '$sticker' to available letters";
+                        $available{$_}++
+                            for $sticker =~ /./g;
+                        ++$n_stickers_used;
+                    } until $available{$letter}
+                        >= $needed{$letter};
+                }
+                say "available letters now: ",
+                    join " ",
+                        map "$_:$available{$_}",
+                            sort keys %available;
+            }
+
+            if ( $available{$letter} && $available{$letter} >= $needed{$letter} ) {
+                # Use available letters.
+                say "using $needed{$letter} available letters '$letter'";
+                $available{$letter} -= $needed{$letter};
+                delete $available{$letter}
+                    if $available{$letter} == 0;
+                delete $needed{$letter};
+                $resolved_a_letter = 1;
+            }
+        }
+        unless ( $resolved_a_letter ) {
+            # For the remaining letters, we need to decide which of several
+            # possible stickers we want to take.
+            # This optimizing process is NOT YET IMPLEMENTED.
+            say "Giving up on this one for now.";
+            return 0;
+        }
+    }
+    return $n_stickers_used;
+}
+
+
+use lib '.';
+use TestExtractor;
+run_tests();
+
+
+__DATA__
+
+Test 1:
+Input: @stickers = ('bubble', 'aaron'), $word = 'bubba'
+Output: 2
+Watch out for the same letter appearing several times on the same sticker.