散列的键值对没初始化时不要用print打印此值，不要用 . 操作符去连接打印 这个值。

 

     31 delete $vertical_alignment{$anonymous};
     32 print $vertical_alignment{$anonymous}."\n";

err:

Use of uninitialized value in concatenation (.) or string at ./hash_exists_del_func.pl line 32.

 

     31 delete $vertical_alignment{$anonymous};
     32 print $vertical_alignment{$anonymous}."\n";

Use of uninitialized value in print at ./hash_exists_del_func.pl line 32.