part1

09/1.pl

@@ -0,0 +1,43 @@
+use 5.20.0;
+
+my $stream = <>;
+chomp $stream;
+
+$stream = clean_stream($stream);
+
+use Text::Balanced qw/ extract_bracketed /;
+use List::AllUtils qw/ sum /;
+
+use experimental qw/signatures /;
+
+say score( $stream );
+
+sub score($stream,$level=1) {
+
+    $stream =~ s/.*?\{(.*)\}.*?/$1/;
+    my @children;
+    my $extracted;
+    while( length $stream ) {
+        ( $extracted, $stream ) = extract_bracketed( $stream, '{}', qr/,?/ );
+        push @children, $extracted if length $extracted;
+        $stream =~ s/^,|,$//;
+    }
+
+    return sum $level, map { score($_,$level+1) } @children;
+
+
+}
+
+sub clean_stream {
+    my $s = shift;
+
+    return $s unless $s =~ s/^(.*?)<//;
+
+    my $clean = $1;
+
+    while( $s =~ s/^.*?(!!|!>|>)// ) {
+        last if $1 eq '>';
+    }
+
+    return $clean . clean_stream($s);
+}