Add more std functions

lib/Minilisp.pm

@@ -77,17 +77,27 @@ sub tokenize {
 }
 
 my %stdctx = (
-  'add' => sub {
+  '+' => sub {
     my $sum = 0;
     $sum += $_ foreach (@_);
     return $sum;
   },
-  'sub' => sub {
+  '-' => sub {
     my $sum = shift;
     $sum -= $_ foreach (@_);
     return $sum;
   },
-  'print' => sub {
+  '*' => sub {
+    my $prod = 1;
+    $prod *= $_ foreach(@_);
+    return $prod;
+  },
+  '/' => sub {
+    my $quot = shift;
+    $quot /= $_ foreach(@_);
+    return $quot;
+  },
+  'write-line' => sub {
     my $e = shift;
     print "$e\n";
     return undef;