The 2 standard ways to get the contents of a directory are glob and opendir (followed by readdir and closedir).

Here's an example of the latter:

# Assuming you want to read files in directory $dir
opendir(my $fh, $dir) or die "Can't read directory '$dir' ($!)\n";
my @files = readdir($fh);
closedir($fh);
foreach my $file (@files) {
    next if ($file eq "." or $file eq "..");  # Skip self and parent
    my $path = "$dir/$file";  # Construct full pathname
    if (-f $path) {
        # Do something with regular file $path ...
    } elsif (-d $path) {
        # Do something with subdirectory $path ...
    }
}
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Note that you need to construct the full pathname, since readdir gives you only the basename of each file/subdirectory.