#! /usr/bin/env raku

my $value = 0;

loop
{
  given prompt "[$value]: "
  {
    when "q" | "quit"   { last; }
    when "d" | "double" { double; }
    when "h" | "half"   { half; }
    when "c" | "clear"  { clear; }
    when /^(\d)$/       { set($0.Int); }
    when "help"         { help; }
  }  
}

sub double
{
  $value *= 2;
}

sub half
{
  $value /= 2;
}

sub clear
{
  $value = 0;
}

sub set ($new)
{
  $value = $new;
}

sub help
{
  say "Please consult a doctor.";
}