#! /usr/bin/env perl
use v6;

my %operators =
  ( '+' => sub { [+] @_ },
    '-' => sub { [-] @_ },
    '*' => sub { [*] @_ },
    '/' => sub { [/] @_ },
  );

grammar rpn_data {
  rule value      { -?\d+ }
  rule operator   { <[+*/\-]> }
  rule expression { }
}

sub rpn_eval (Str $e) returns Num {
  my @stack;
#  die "Invalid RPN: $e" unless $e ~~ /<expression>/;
  for $e.split() -> $tok {
    if $tok ~~ /<value> / { @stack.push($tok); next }
    @stack.push(%operators{$tok}(reverse @stack.pop, @stack.pop));
  }
  @stack[0]
}

say rpn_eval($_) while $_ = =<>