cmd: Fixed var substring in 'enableDelayedExpansion' mode.

programs/cmd/tests/test_builtins.cmd

@@ -1275,6 +1275,17 @@ set x=C:\Program Files (x86)
 if ""=="" set y=%x%\dummy
 echo %y%
 
+echo --- Testing if + var subst in delayed expansion mode
+setlocal enableDelayedExpansion
+for %%i in (abc 10.0 11.0) do (
+    set result=%%i
+    echo [DEBUG] checking {!result!}
+    if "!result:~0,3!"=="10." (
+        echo SDKVER=!result!
+    )
+)
+endlocal
+
 echo ------------ Testing for ------------
 echo --- plain FOR
 for %%i in (A B C) do echo %%i

programs/cmd/tests/test_builtins.cmd.exp

@@ -927,6 +927,11 @@ x@space@
 A
 ------------ Testing if/set ------------
 C:\Program Files (x86)\dummy
+--- Testing if + var subst in delayed expansion mode
+[DEBUG] checking {abc}
+[DEBUG] checking {10.0}
+SDKVER=10.0
+[DEBUG] checking {11.0}
 ------------ Testing for ------------
 --- plain FOR
 A

programs/cmd/wcmdmain.c

@@ -596,7 +596,7 @@ static WCHAR *WCMD_expand_envvar(WCHAR *start, WCHAR startchar)
     /* If there's complex substitution, just need %var% for now
        to get the expanded data to play with                    */
     if (colonpos) {
-        *colonpos = startchar;
+        *colonpos = '%';
         savedchar = *(colonpos+1);
         *(colonpos+1) = 0x00;
     }