Bug in AC_CACHE_VAL (maybe)

[Tim Van Holder]

Current CVS autoconf run for help2man 1.24, out-of the box yields:

configure.in:5: m4.exe: Warning: Too few arguments to built-in `m4_regexp'
configure.in:5: m4.exe: Warning: Too few arguments to built-in `m4_if'

The likely culprit seems to be AC_CACHE_VAL.
Below are the contents of aclocal.m4 (after autoupdating and removing the
spurious '([])' from AS_MESSAGE_LOG_FD).
My guess is that the ifelse is being executed by the check for AC_DEFINE
in the second part of AC_CACHE_VAL. Question is: is this a bonafide
autoconf bug, or simply a broken user-defined macro (and if the latter,
what is the proper way to write this macro)?

== aclocal.m4 starts here
changequote()
define(RIGHT_BRACKET, ])
changequote([, ])

dnl AC_PROG_PERL([MIN-VERSION])
AC_DEFUN(AC_PROG_PERL,
[# find perl binary
AC_MSG_CHECKING([for perl])
AC_CACHE_VAL(ac_cv_prog_PERL,
[ifelse([$1],,,[echo "configure:__oline__: ...version $1 required" 
>&AS_MESSAGE_LOG_FD
  ])# allow user to override
  if test -n "$PERL"; then
    ac_try="$PERL"
  else
    ac_try="perl perl5"
  fi

  for ac_prog in $ac_try; do
    echo "configure:__oline__: trying $ac_prog" >&AS_MESSAGE_LOG_FD
    if ($ac_prog -e 'printf "found version %g\n",$]RIGHT_BRACKET[dnl
ifelse([$1],,,[;exit($]RIGHT_BRACKET[<$1)])') 1>&AS_MESSAGE_LOG_FD 2>&1; then
      ac_cv_prog_PERL=$ac_prog
      break
    fi
  done])dnl
PERL="$ac_cv_prog_PERL"
if test -n "$PERL"; then
  AC_MSG_RESULT($PERL)
else
  AC_MSG_RESULT(no)
fi
AC_SUBST(PERL)dnl
])dnl