updated for version 7.4.423
Problem: expand("$shell") does not work as documented.
Solution: Do not escape the $ when expanding environment variables.
diff --git a/src/vim.h b/src/vim.h
index cb2a9e5..2a6d9a0 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -835,6 +835,7 @@
#define EW_ICASE 0x100 /* ignore case */
#define EW_NOERROR 0x200 /* no error for bad regexp */
#define EW_NOTWILD 0x400 /* add match with literal name if exists */
+#define EW_KEEPDOLLAR 0x800 /* do not escape $, $var is expanded */
/* Note: mostly EW_NOTFOUND and EW_SILENT are mutually exclusive: EW_NOTFOUND
* is used when executing commands and EW_SILENT for interactive expanding. */