Index: doc/README.variables
===================================================================
RCS file: /usr/cvsroot/asterisk/doc/README.variables,v
retrieving revision 1.47
diff -u -r1.47 README.variables
--- doc/README.variables	17 Jun 2005 00:33:00 -0000	1.47
+++ doc/README.variables	21 Jun 2005 20:51:13 -0000
@@ -321,7 +335,7 @@
 CONDITIONALS
 ---------------------------
 
-There is one conditional operator - the conditional goto : 
+There is one conditional application - the conditional goto : 
 
 	exten => 1,2,gotoif(condition?label1:label2)
 
@@ -504,6 +518,73 @@
 **    match anywhere in the string. The only diff with the ':' is that
 **    match doesn't have to be anchored to the beginning of the string.
 
+--------------------------------------------------------
+DEBUGGING HINTS FOR $[  ]  EXPRESSIONS
+--------------------------------------------------------
+
+** THE FOLLOWING UTILITIES ARE PROVIDED ONLY FOR SYSTEMS THAT
+** HAVE FLEX-2.5.31 OR GREATER, AND USE THE UPGRADED LEXER!!!
+**
+** There are two utilities you can build to help debug the $[ ] in
+** your extensions.conf file.
+**
+** The first, and most simplistic, is to issue the command:
+**
+** make testexpr2
+**
+** in the top level asterisk source directory. This will build
+** a small executable, that is able to take the first command line
+** argument, and run it thru the expression parser. No variable
+** substitutions will be performed. It might be safest to wrap
+** the expression in single quotes...
+**
+** testexpr2 '2*2+2/2'
+**
+** is an example.
+**
+** And, in the utils directory, you can say:
+**
+** make check_expr
+**
+** and a small program will be built, that will check the file
+** mentioned in the first command line argument, for any expressions
+** that might be have problems when you move to flex-2.5.31.
+** It was originally designed to help spot possible incompatibilities
+** when moving from the pre-2.5.31 world to the upgraded version of
+** the lexer.
+**
+** But one more capability has been added to check_expr, that might
+** make it more generally useful. It now does a simple minded evaluation of
+** all variables, and then passes the $[] exprs to the parser. If there are
+** any parse errors, they will be reported in the log file. You can use
+** check_expr to do a quick sanity check of the expressions in your 
+** extensions.conf file, to see if they pass a crude syntax check.
+**
+** The "simple-minded" variable substitution replaces ${varname} variable
+** references with '555'. You can override the 555 for variable values,
+** by entering in var=val arguments after the filename on the command line.
+** So...
+**
+** check_expr /etc/asterisk/extensions.conf CALLERIDNUM=3075551212 DIALSTATUS=TORTURE EXTEN=121
+**
+** will substitute any ${CALLERIDNUM} variable references with 3075551212, any ${DIALSTATUS} 
+** variable references with 'TORTURE', and any ${EXTEN} references with '121'.
+** If there is any fancy stuff going on in the reference, like ${EXTEN:2}, then the
+** override will not work. Everything in the ${...} has to match. So, to substitute
+** #{EXTEN:2} references, you'd best say:
+**
+** check_expr /etc/asterisk/extensions.conf CALLERIDNUM=3075551212 DIALSTATUS=TORTURE EXTEN:2=121
+**
+** on stdout, you will see something like:
+**
+** OK -- $[ "${DIALSTATUS}"  = "TORTURE" | "${DIALSTATUS}" = "DONTCALL" ] at line 416
+**
+** In the expr2_log file that is generated, you will see:
+**
+** line 416, evaluation of $[  "TORTURE"  = "TORTURE" | "TORTURE" = "DONTCALL"  ] result: 1
+**
+** check_expr is a very simplistic algorithm, and it is far from being guaranteed 
+** to work in all cases, but it is hoped that it will be useful.
 
 ---------------------------------------------------------
 Asterisk standard channel variables