class Byebug::TraceCommand

def execute
  if @match[1] =~ /on|off/
    onoff = 'on' == @match[1]
    Byebug.tracing = onoff
    print "#{show_setting('linetrace')}\n"
  elsif @match[1] =~ /var(?:iable)?/
    varname = @match[2]
    if debug_eval("defined?(#{varname})")
      if @match[3] && @match[3] !~ /(:?no)?stop/
        errmsg "expecting \"stop\" or \"nostop\"; got \"#{@match[3]}\"\n"
      else
        dbg_cmd = (@match[3] && @match[3] !~ /nostop/) ? 'byebug(1,0)' : ''
      end
      eval("trace_var(:#{varname}) do |val|
              print \"traced variable \#{varname} has value \#{val}\n\"
              #{dbg_cmd}
            end")
    else
      errmsg "#{varname} is not a global variable.\n"
    end
  else
    errmsg "expecting \"on\", \"off\", \"var\" or \"variable\"; got: " \
           "\"#{@match[1]}\"\n"
  end
end