diff --git a/src/fsh.nim b/src/fsh.nim
index 42b87c5..a2906eb 100644
--- a/src/fsh.nim
+++ b/src/fsh.nim
@@ -10,7 +10,8 @@ import os
 import strutils
 
 # globals
-var shellVariables = newStringTable(modeCaseSensitive)
+# shellVariables are an array of vars
+var shellVariables = @[newStringTable(modeCaseSensitive)]
 # Environment variables get defined in a separate var
 var envVariables = newStringTable(modeCaseSensitive)
 # populate the table
@@ -191,9 +192,9 @@ proc readVariable(strm: Stream): string =
 # evalVariable finds a value of a variable
 proc evalVariable(vari: string): string =
   if vari == "$": return "$"
-  if shellVariables.hasKey(vari):
-    result=shellVariables[vari]
-  elif envVariables.hasKey(vari):
+  for frame in shellVariables:
+    if frame.hasKey(vari): return frame[vari]
+  if envVariables.hasKey(vari):
     result = envVariables[vari]
   else:
     raise newShellVariableException("No such variable", vari)
@@ -252,7 +253,7 @@ proc runBuiltin(builtin: string, args: openArray[string]): (string, int) =
     of "set":
       if args.len < 2:
         raise newShellCommandException("Not enough arguments provided", "set")
-      shellVariables[args[0]] = args[1..^1].join(" ")
+      shellVariables[0][args[0]] = args[1..^1].join(" ")
       return ("", 0)
     of "setenv":
       if args.len < 2:
@@ -310,16 +311,16 @@ proc runBuiltin(builtin: string, args: openArray[string]): (string, int) =
     of "cd":
       try:
         if args.len == 0:
-          shellVariables["LASTPWD"] = getCurrentDir()
+          shellVariables[shellVariables.high]["LASTPWD"] = getCurrentDir()
           setCurrentDir(getHomeDir())
           return ("", 0)
         else:
           if args[0] == "-":
             let LASTPWD = getCurrentDir()
-            setCurrentDir(shellVariables["LASTPWD"])
-            shellVariables["LASTPWD"] = LASTPWD
+            setCurrentDir(shellVariables[shellVariables.high]["LASTPWD"])
+            shellVariables[shellVariables.high]["LASTPWD"] = LASTPWD
             return ("", 0)
-          shellVariables["LASTPWD"] = getCurrentDir()
+          shellVariables[shellVariables.high]["LASTPWD"] = getCurrentDir()
           setCurrentDir(args[0])
           return ("", 0)
       except OsError as e:
@@ -374,12 +375,12 @@ when isMainModule:
   setControlCHook(ctrlc)
   let stdinstrm = stdin.newFileStream
   # Set the default prompt
-  shellVariables["PROMPT"] = "$PWD \\$"
-  stdout.write(shellVariables["PROMPT"].newStringStream.substitute)
+  shellVariables[shellVariables.high]["PROMPT"] = "$PWD \\$"
+  stdout.write(shellVariables[shellVariables.high]["PROMPT"].newStringStream.substitute)
   while not stdinstrm.atEnd():
     try:
       discard stdinstrm.readCommand.execute
-      stdout.write(shellVariables["PROMPT"].newStringStream.substitute)
+      stdout.write(shellVariables[shellVariables.high]["PROMPT"].newStringStream.substitute)
     except ShellError, ShellCommandError, ShellVariableError:
       let e = getCurrentException()
       stderr.write(e.msg, "\n")