diff --git a/Cargo.lock b/Cargo.lock
index 7e0d1bc..6c36619 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -22,7 +22,7 @@ checksum = "b03f7fbd470aa8b3ad163c85cce8bccfc11cc9c44ef12da0a4eddd98bd307352"
 
 [[package]]
 name = "spl"
-version = "0.3.1"
+version = "0.3.2"
 dependencies = [
  "multicall",
  "once_cell",
diff --git a/pure.spl b/pure.spl
new file mode 100644
index 0000000..e286e40
--- /dev/null
+++ b/pure.spl
@@ -0,0 +1,48 @@
+"#stream.spl" import
+
+"uses less native functions where possible";
+
+func pop { | with _ ; }
+
+func dup { x x | with x ;
+    x x
+}
+
+func swap { b a | with a b ;
+    b a 
+}
+
+func not { !x | with x ;
+    1 
+    x if { pop 0 }
+}
+
+func and { a&&b | with a b ;
+    0
+    a if { b if { pop 1 } }
+}
+
+func or { a||b | with a b ;
+    0
+    a if { pop 1 }
+    b if { pop 1 }
+}
+
+func alit-end { array | with type ;
+    def array 0 anew =array
+    while { dup type eq not } {
+        0 1 anew dup:set; array aadd =array
+    }
+    pop array
+}
+
+func read-file { str | with path ; 
+    def stream path 0 StreamTypes:file:create =stream
+    1024 stream:read-to-end:to-str
+}
+
+func acopy { | with from to idxsrc idxdst len ;
+    len:foreach<{ | with i ;
+        i idxsrc + from:get i idxdst + to:set;
+    }>
+}
diff --git a/src/runtime.rs b/src/runtime.rs
index 9f8bbad..7004303 100644
--- a/src/runtime.rs
+++ b/src/runtime.rs
@@ -46,6 +46,15 @@ pub fn runtime_mut<T>(f: impl FnOnce(RwLockWriteGuard<Runtime>) -> T) -> T {
     })
 }
 
+pub fn fork_runtime() -> Arc<Mut<Runtime>> {
+    RUNTIME.with(|rt| {
+        rt.borrow_mut()
+            .as_mut()
+            .expect("no runtime (use .set)")
+            .clone()
+    })
+}
+
 pub fn get_type(name: &str) -> Option<AMType> {
     runtime(|rt| rt.get_type_by_name(name))
 }
@@ -784,7 +793,7 @@ impl Words {
 #[derive(Clone)]
 pub enum FuncImpl {
     Native(fn(&mut Stack) -> OError),
-    NativeDyn(Arc<Box<dyn Fn(&mut Stack) -> OError>>),
+    NativeDyn(Arc<Box<dyn (Fn(&mut Stack) -> OError) + Send + Sync>>),
     SPL(Words),
 }
 
diff --git a/src/std_fns.rs b/src/std_fns.rs
index 0d3c44d..d1ccaeb 100644
--- a/src/std_fns.rs
+++ b/src/std_fns.rs
@@ -7,6 +7,7 @@ use std::{
     ops::{Add, Div, Mul, Rem, Sub},
     process::{self, Stdio},
     sync::Arc,
+    thread,
 };
 
 use crate::{dyn_fns, mutex::Mut, runtime::*, sasm::sasm_write, *};
@@ -840,9 +841,22 @@ pub fn write_file_sasm(stack: &mut Stack) -> OError {
     Ok(())
 }
 
+pub fn fork(stack: &mut Stack) -> OError {
+    require_on_stack!(callable, Func, stack, "fork");
+    let mut new_stack = stack.clone();
+    let rt = fork_runtime();
+    thread::spawn(move || {
+        rt.set();
+        if let Some(err) = new_stack.call(&callable).err() {
+            println!("{err:?}");
+        };
+    });
+    Ok(())
+}
+
 pub fn register(r: &mut Stack, o: Arc<Frame>) {
     type Fn = fn(&mut Stack) -> OError;
-    let fns: [(&str, Fn, u32); 53] = [
+    let fns: [(&str, Fn, u32); 54] = [
         ("pop", pop, 0),
         ("dup", dup, 2),
         ("clone", clone, 1),
@@ -896,6 +910,7 @@ pub fn register(r: &mut Stack, o: Arc<Frame>) {
         ("throw", throw, 0),
         ("write-sasm", write_sasm, 1),
         ("write-file-sasm", write_file_sasm, 1),
+        ("fork", fork, 0),
     ];
     for f in fns {
         r.define_func(
diff --git a/src/stream.rs b/src/stream.rs
index eb53db9..1e14867 100644
--- a/src/stream.rs
+++ b/src/stream.rs
@@ -45,13 +45,13 @@ impl StreamType {
 
 /// An SPL stream, holding a reader and a writer, and a function to close it.
 pub struct Stream {
-    reader: Box<dyn Read + 'static>,
-    writer: Box<dyn Write + 'static>,
+    reader: Box<dyn Read + Send + Sync + 'static>,
+    writer: Box<dyn Write + Send + Sync + 'static>,
     close: fn(&mut Self),
 }
 
 impl Stream {
-    pub fn new<T: Read + Write + 'static>(main: T, close: fn(&mut Self)) -> Self {
+    pub fn new<T: Read + Write + Send + Sync + 'static>(main: T, close: fn(&mut Self)) -> Self {
         let mut rw = Box::new(main);
         Self {
             // SAFETY: Because these are both in private fields on one object, they can not be
@@ -63,8 +63,8 @@ impl Stream {
         }
     }
     pub fn new_split(
-        reader: impl Read + 'static,
-        writer: impl Write + 'static,
+        reader: impl Read + Send + Sync + 'static,
+        writer: impl Write + Send + Sync + 'static,
         close: fn(&mut Self),
     ) -> Self {
         Self {
diff --git a/std.spl b/std.spl
index 3778f31..2d2345c 100644
--- a/std.spl
+++ b/std.spl
@@ -12,7 +12,7 @@ func print { |
 }
 
 func println { |
-    print "\n" print
+    "\n" concat print
 }
 
 construct error {
@@ -141,7 +141,7 @@ construct _array-ext {
         this:len -- this:get
     }
     =last { | with this ;
-        this:len -- this:set
+        this:len -- this:set;
     }
     0 { any | with this ;
         0 this:get
diff --git a/test.spl b/test.spl
index e5c5045..3ae0d51 100644
--- a/test.spl
+++ b/test.spl
@@ -150,6 +150,16 @@ func main { int | with args ;
     "testmsg2" bus:publish
     "testmsg1" bus:publish
     "testmsg3" bus:publish
+
+    "" println
+    "testing threads" println
+
+    def other-thread-done 0 =other-thread-done
+    { |
+        "i am in the other thread!!!" println
+        1 =other-thread-done
+    } fork
+    while { other-thread-done not } { "waiting for the other thread..." println }
     
     100
 }