How It Works

1. Parameter Handling:
   The function accepts one or more paths (via the -Path parameter or through the pipeline). It also accepts a -Recurse switch to control whether subdirectories are searched.

2. Input Validation:
   Each provided path is checked with Test-Path. If a path does not exist, a warning is emitted and that path is skipped.

3. Parallel Enumeration:
   For each valid path, a [System.IO.DirectoryInfo] object is created. The directories and files are enumerated using EnumerateDirectories and EnumerateFiles respectively, then converted into a parallel query using AsParallel.

4. Output:
   The function concatenates the directories and files found and outputs them as a single collection.