(A possible bug in Apache is now suspected ... see below.)
Here's the statements: (Apache 2.4)
<IfDefine !SERVER_TYPE>
Define SERVER_TYPE prod
</IfDefine>
<If "${SERVER_TYPE} !~ /prod|demo|test/"> <===error here===
Error "Define 'SERVER_TYPE' is hosed'"
</If>
Apache complains about the IF:
Cannot parse condition clause: syntax error, unexpected T_OP_NRE, expecting '('
I can guess that T_OP_NRE refers to "negated regular-expression" i.e. "!~" but I can't for the life of me figure out what's the syntax-error in that statement! (And, incidentally, "=~" produces [almost] the same message.)
Apache is recognizing the ${SERVER_TYPE} syntax as I can confirm if I misspell the identifier. The documentation for <DEFINE> expressly states that "${ident}" not "%{ident}" syntax should be used, as I have done.
What's wrong with my syntax, and why does Apache expect a left-parenthesis?
I am cautiously beginning to believe that this is actually a BUG(!) in Apache/2.4.12 because the parse-error only occurs when "${DEFINED_SYMBOL}" is used. It will complain and do all the right things if the symbol is not defined (so, it knows what it's looking at ...), but it gives a nonsensical (to me ...) message as-shown if, and only if, this construct is on the left-hand side.
An apparent workaround is to put the symbol in single quotes, e.g.:
<If "'${SERVER_TYPE}' != /prod/demo/test/">
... but so-far in my testing I don't think that it is matching the regex correctly. In fact, I'm not yet sure what is going on, because the following is considered to be a non-match ("true"):
<If "'prod' !~ /prod|demo|test/">
The regex syntax can be shown to be correct via this Perl one-liner:
perl -e 'my $var = "prod"; if ($var =~ /prod|demo|test/) {print "yes\n";}'
... which prints "yes."
P.S. The "${IDENT}" syntax is correct (versus "%{}", which is not) in the case of a Defined symbol.
