part1

18/1.pl

@@ -0,0 +1,51 @@
+use 5.20.0;
+
+my @commands = <>;
+
+my $i = 0;
+
+my %reg;
+my $last_played;
+
+use experimental qw/ signatures /;
+
+sub valof($x) {
+    my $y = $x =~ /\d/ ? $x : $reg{$x};
+    die $_ if $y eq 'Inf';
+    return $y;
+}
+
+my $vr = qr/(-?\d+|.)/;
+
+while() {
+    $_ = $commands[$i++];
+    warn $_ if /\bb\b/;
+    if( /snd (.)/ ) {
+        $last_played = valof($1);
+    }
+    elsif( /set (.) $vr/ ) {
+        $reg{$1} = valof($2);
+    }
+    elsif( /add (.) $vr/ ) {
+        $reg{$1} += valof($2);
+    }
+    elsif( /mul (.) $vr/ ) {
+        $reg{$1} *= valof($2);
+    }
+    elsif( /mul (.) $vr/ ) {
+        $reg{$1} *= valof($2);
+    }
+    elsif( /mod (.) $vr/ ) {
+        $reg{$1} %= valof($2);
+    }
+    elsif( /jgz (.) $vr/ ) {
+        next unless $reg{$1} > 0;
+        $i += -1 + valof($2);
+    }
+    elsif( /rcv (.)/ ) {
+        next unless $reg{$1};
+        die $last_played;
+    }
+    else { die "wut? $_"; }
+
+}

18/input.txt

@@ -0,0 +1,41 @@
+set i 31
+set a 1
+mul p 17
+jgz p p
+mul a 2
+add i -1
+jgz i -2
+add a -1
+set i 127
+set p 622
+mul p 8505
+mod p a
+mul p 129749
+add p 12345
+mod p a
+set b p
+mod b 10000
+snd b
+add i -1
+jgz i -9
+jgz a 3
+rcv b
+jgz b -1
+set f 0
+set i 126
+rcv a
+rcv b
+set p a
+mul p -1
+add p b
+jgz p 4
+snd a
+set a b
+jgz 1 3
+snd b
+set f 1
+add i -1
+jgz i -11
+snd a
+jgz f -16
+jgz a -19