diff --git a/Cargo.toml b/Cargo.toml
index 92b308d..c816dc1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,8 @@ clap = { version = "^4", features = ["derive"] }
 
 rayon = "^1"
 
+once_cell = "^1"
+
 mago-syntax = "^1.13"
 mago-interner = "^1.0.0-alpha"
 mago-source = "^1.0.0-alpha"
@@ -18,4 +20,5 @@ mago-names = "^1.13"
 mago-project = "^0.26"
 mago-semantics = "^1.13"
 
+regex = "^1"
 walkdir = "^2"
diff --git a/src/cli/flags.rs b/src/cli/flags.rs
index e763160..a7d5e2c 100644
--- a/src/cli/flags.rs
+++ b/src/cli/flags.rs
@@ -12,20 +12,35 @@ use crate::util::fs;
 #[derive(Parser, Debug)]
 #[command(name = "pmp", about, version)]
 pub struct Args {
-    #[arg(long, value_hint = FilePath, value_parser = fs::path_exists)]
+    #[arg(long, value_hint = FilePath, value_parser = fs::path_exists, help = "Path to PHP binary")]
     php: Option<PathBuf>,
 
     #[arg(long, short = 'd', hide = true)]
     debug: bool,
-    #[arg(long, short = 'v')]
+    #[arg(long, short = 'v', help = "Verbose output")]
     verbose: bool,
+    #[arg(long, short = 'n', help = "Dry run, does not modify files or cache")]
+    dry_run: bool,
 
-    #[arg(default_value_os = OsStr::new("."), value_hint = FilePath, value_parser = fs::path_exists)]
+    #[arg(long, short = 'e', value_hint = FilePath, value_parser = fs::path_exists, default_values_os = [OsStr::new(".gitignore"), OsStr::new("vendor/")], help = "Exclude files from pre-processing, e.g. vendor/")]
+    exclude: Vec<PathBuf>,
+    #[arg(long, short = 'c', value_hint = FilePath, value_parser = fs::valid_possible_path, default_value_os = OsStr::new(".cache"), help = "Cache directory location")]
+    cache_dir: Option<PathBuf>,
+    #[arg(long, short = 'o', value_hint = FilePath, value_parser = fs::valid_possible_path, default_value_os = OsStr::new("."), help = "Output directory location")]
+    output_dir: Option<PathBuf>,
+    #[arg(long, short = 'i', conflicts_with = "dry_run", help = "Invalidate cache and re-process all files")]
+    invalidate_cache: bool,
+
+    #[arg(value_hint = FilePath, value_parser = fs::path_exists, default_value_os = OsStr::new("."), help = "Directory to recursively scan and pre-process")]
     directory: Option<PathBuf>,
     #[arg(last = true)]
     passthrough: Vec<String>,
 }
 
+// todo: ignore .gitignore marked content per default
+// todo: diff output with verbose and ofc trace for warnings/errors
+// todo: cache with file hashes and system last edited timestamp
+
 impl Args
 {
     pub fn parse() -> Self {
diff --git a/src/util/fs.rs b/src/util/fs.rs
index 2611755..29a2fd2 100644
--- a/src/util/fs.rs
+++ b/src/util/fs.rs
@@ -1,6 +1,27 @@
+use regex::Regex;
 use std::path::PathBuf;
+use once_cell::sync::Lazy;
+
+static PATH_REGEX: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(r"^[+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?$").unwrap()
+});
 
 pub fn path_exists(s: &str) -> Result<PathBuf, String> {
     let p = PathBuf::from(s);
     p.exists().then_some(p).ok_or("path does not exist".to_string())
 }
+
+pub fn valid_possible_path(s: &str) -> Result<PathBuf, String>
+{
+    let lower = s.to_ascii_lowercase();
+
+    if lower == "true" || lower == "false" {
+        return Err("boolean literal is not allowed".into());
+    }
+
+    if PATH_REGEX.is_match(s) {
+        return Err("numeric literal is not allowed".into());
+    }
+
+    Ok(PathBuf::from(s))
+}