perl打开文件名中包含变量的文件

I try to open a list of files in a folder. Eventually I want to insert a HTML-Snippet in it. So far I can open the folder and read the list in an array. That´s fine. But when I try to open the files by using a variable as filename, I get an error message every time ("permission denied"). No matter if I use $_ or other variations of putting the values of list items in variables. I have found similar questions here, but didnt find the solution so far. Here is my code:I try to open a list of files in a folder. Even