added perl function support

README.md

@@ -156,10 +156,26 @@ function name:
     470
     220
     res2vcc
+    => 2.79
 
 You  can  also  put  the   function  definition  in  the  config  file
 `~/.rpnc`. Empty lines and lines beginning with `#` will be ignored.
 
+Another way  to define a  function is to  use perl code  directly. The
+perl code must  be a closure string and surrounded  by braces. You can
+access the stack via `@_`.  Here's an example:
+
+    f pr { return "1.0 / (" . join(' + ', map { "1.0 / $_"} @_) . ")" }
+    
+This  function  calculates the  parallel  resistance  of a  number  of
+resistors. It adds up all values from the stack. Usage:
+
+    22
+    47
+    330
+    pr
+    => 41.14
+
 
 ## Using STDIN via a PIPE
 

rpnc

@@ -157,12 +157,6 @@ my %func    = (
                  }
                },
 
-               'pr' => sub {
-                 # parallel resistance, maybe add ~/.rpncrc support
-                 # where to add such custom functions...
-                 return "1 / (" . join(' + ', map { "1 / $_"} @_) . ")";
-               },
-
                'm' => sub {
                  # median
                  if (scalar @_ >= 2) {
@@ -571,11 +565,17 @@ sub defun {
 
   $custom{$name} = "@tokens";
 
+  if ($custom{$name} =~ /^\{.*\}$/) {
+    # perl code
+    $func{$name} = sub { return eval "@tokens" };
+  }
+  else {
+    # rpnc code
     $func{$name} = sub {
       my $max = scalar @_;
       my @args = reverse(@_);
 
-    # replace N1..NN with actual args
+      # replace N1..NN with actual stack items
       my @body;
       foreach my $item (@tokens) {
         if ($item =~ /^([A-Z])(\d+)$/) {
@@ -597,6 +597,7 @@ sub defun {
       # execute @body
       looptokenize("@body");
     };
+  }
 
   print "function $name() defined.\n" unless $silent;
 }
@@ -646,5 +647,6 @@ Various Commands:                         Functions:
  h    show history of past operations     fs    show list of defined functions
  q    finish (C-d works as well)          Using register: enter R + index, e.g. R1
  ?    print help                          Constants: PI V2 V3
+
 ~;
 }