[wip] Added rpn calculator

wip/rpm.p6

@@ -0,0 +1,28 @@
+#!/usr/bin/perl6
+
+# RPN calulator from the bottom of http://use.perl.org/~pmichaud/journal/38580
+
+# Excellent example, not sure where/if it fits
+
+use v6;
+
+my %op_dispatch_table = {
+    '+'    => { .push(.pop + .pop)  },
+    '-'    => { .push(.pop R- .pop) },
+    '*'    => { .push(.pop * .pop)  },
+    '/'    => { .push(.pop R/ .pop) },
+    'sqrt' => { .push(.pop.sqrt)    },
+};
+
+sub evaluate (%odt, $expr) {
+    my @stack;
+    my @tokens = $expr.split(/\s+/);
+    for @tokens {
+        when /\d+/     { @stack.push($_); }
+        when ?%odt{$_} { %odt{$_}(@stack); }
+        default        { die "Unrecognized token '$_'; aborting"; }
+    }
+    @stack.pop;
+}
+
+say "Result: { evaluate(%op_dispatch_table, @*ARGS[0]) }";