Perl recursively iterates through the files in the directory

#! / usr / bin / perl -w
use strict;
use File :: Spec;

local $ \ = "\ n"; # Add a newline character to the output of each line of the current module

my% options;

#Directory path
$ options {single_case} = ‘/ home / jiangyu / src / pl / Example’;

   my @cases;
    if (-d $ options {single_case}) {# Determine whether the directory exists
        my @files;
        my $ dh;
        push (@files, $ options {single_case});
        while (@files) {
            if (-d $ files [0]) {#If it is a directory, perform the following operations
                opendir $ dh, $ files [0] or die $ !; #Open the directory handle and print an error message if it fails
                @_ = grep {/^[^\.]/} readdir $ dh; #filter out files with "." and "..", which are hidden files under UNIX
                foreach (@_) {
                    push (@files, File :: Spec-> catfile ($ files [0], $ _)); #Connect directory name and file name to form a complete file path:
                }
                closedir $ dh;
            }
            #If the file is directly pressed into the array @cases
            elsif ($ files [0] = ~ /\.t$/) {
                push (@cases, $ files [0]);
            }
            shift @files;
        }
    }
    else {
        @cases = ($ options {single_case});
    }


print $ _ foreach @cases; #print file list