class Byebug::TracevarCommand

def execute
  var = @match[1]
  return errmsg(pr('trace.errors.needs_global_variable')) unless var
  unless global_variables.include?(:"#{var}")
    return errmsg(pr('trace.errors.var_is_not_global', name: var))
  end
  stop = @match[2] && @match[2] !~ /nostop/
  instance_eval do
    trace_var(:"#{var}") { |val| on_change(var, val, stop) }
  end
  puts pr('trace.messages.success', var: var)
end