fall back on shell command behaviour for undefined variables

Signed-off-by: Ava Hahn <ava@sunnypup.io>

src/stl/posix.rs

@@ -60,6 +60,8 @@ use {
     },
 };
 
+pub const POSIX_LOAD_NAME: &str = "load";
+
 pub struct ShellState {
     pub parent_pid: Pid,
     pub parent_sid: Pid,
@@ -190,7 +192,7 @@ fn launch_command(
             .stdin(infd)
             .stdout(outfd)
             .stderr(errfd)
-        .process_group(0)
+            .process_group(0)
             .spawn();
     }
 
@@ -273,7 +275,7 @@ const LOAD_DOCSTRING: &str = "Calls a binary off disk with given arguments.
 Arguments may be of any type except lambda. If a symbol is not defined it will be passed as a string.
 first argument (command name) will be found on path (or an error returned).
 
-examples:
+examples:call
     (l ping google.com)
     (let ((ping-count 4))
       (l ping -c ping-count google.com))
@@ -787,7 +789,7 @@ pub fn load_posix_shell(syms: &mut SymTable, shell_state: Rc<RefCell<ShellState>
     syms.insert(
         String::from("l"),
         Symbol {
-            name: String::from("load"),
+            name: String::from(POSIX_LOAD_NAME),
             args: Args::Infinite,
             conditional_branches: true,
             docs: String::from(LOAD_DOCSTRING),
@@ -799,9 +801,9 @@ pub fn load_posix_shell(syms: &mut SymTable, shell_state: Rc<RefCell<ShellState>
     );
 
     syms.insert(
-        String::from("load"),
+        String::from(POSIX_LOAD_NAME),
         Symbol {
-            name: String::from("load"),
+            name: String::from(POSIX_LOAD_NAME),
             args: Args::Infinite,
             conditional_branches: true,
             docs: String::from(LOAD_DOCSTRING),