用字符串对列表赋值，一个字符串对应一个列表元素，eg: my @escaped = "asteriskasterisk hash access unpack_func";

my @escaped = "asteriskasterisk hash access unpack_func";     　　# 是一个元素的赋值

25 unless( $escaped[1] ){
     26     print "\$escaped[1] is undef.";
     27 }

输出：$escaped[1] is undef.