Updated Environment (markdown)

Environment.md

@@ -1,4 +1,4 @@
-The `$MPW/Environment.text` file contains environment variables used by some MPW programs. Particularly, header file locations are defined here.
+The `$MPW/Environment.text` file contains environment variables used by some MPW programs. Particularly, header file locations are defined here.  Additionally, variable expansion occurs during pathname conversion, so `mpw Link ... {Libraries}ToolLibs.o` works as expected.
 
 The file format is:
 
@@ -21,10 +21,30 @@ Variables are expanded within the value.  Recognized forms are:
 * `${name}`
 * `{name}`
 
+## Example 
+
+    MPWVersion ?= 3.2
+
+    ShellDirectory=$MPW
+    SysTempFolder=/tmp/
+    TempFolder=/tmp/
+
+    AIIGSIncludes={MPW}Interfaces:AIIGSIncludes:
+    RIIGSIncludes={MPW}Interfaces:RIIGSIncludes:
+    CIIGSIncludes={MPW}Interfaces:CIIGSIncludes:
+    CIIGSLibraries={MPW}Libraries:CIIGSLibraries:
+    PIIGSIncludes={MPW}Interfaces:PIIGSIncludes:
+    PIIGSLibraries={MPW}Libraries:PIIGSLibraries:
+
 
 ## Command line 
 
 Variables can also be defined as part of the mpw command. eg:
+
     mpw -DMPWVersion=3.5 SC ...
 
-These variables are processed after internal variables are set (`$Command`) but before the `Environment.text` file is loaded. 
+These variables are processed after internal variables are set (`$MPW` and `$Command`) but before the `Environment.text` file is loaded. This allows for fast switching between different versions of MPW headers and libraries:
+
+    Libraries={MPW}Libraries:Libraries-{MPWVersion}:
+    PLibraries={MPW}Libraries:PLibraries-{MPWVersion}:
+    CLibraries={MPW}Libraries:CLibraries-{MPWVersion}: