TCL函数抛出错误

Question

我有这个功能，

proc get_sys_status aname {
upvar $aname a

set input [exec "get system status\n" "# "]
set linelist [split $input \n]
foreach line $linelist 
{
    if {![regexp {([^:]+):(.*)} $line dummy key value]} 
        continue
    switch -regexp -- $key 
    {
        Hostname 
        {
            set a(hostname) [string trim $value]
        } 
    }
}
}

get_sys_status status
 
# line 17
puts "This machine is called $status(hostname)" 

一般的想法是它接受命令“get system status”的输出并解析数据。解析之后，它会抓取主机名并使用它来向框发出一些命令。第17行（最后一行）出现错误：

can't read "status(hostname)": no such variable

----An error occured at line #17 of the script----

------- The end of log ----------

这个功能出了什么问题？