AC_PATH_PROG fails in 2.53?

[Stephen Booth]

I'm having a very strange problem since I upgraded to 2.53 this morning.  I 
have some m4 code that previously worked under autoconf-2.52 but now it fails 
under 2.53.  I'm trying to check for the script cgicc-config in the given path. 
 configure is failing with the message

configure: error: cgicc-config not found in 
/tmp/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/usr/bin:/usr/X11R6/bin:/usr/mozilla:/usr/mysql/bin:/home/sbooth/bin:/usr/X11R6/bin:/usr/mozilla:/usr/mysql/bin:/home/sbooth/bin
make: *** [config.status] Error 1

but

% ls -l /tmp/bin/
total 4
-rwxr-xr-x    1 sbooth   sbooth       2204 Mar  9 11:46 cgicc-config*


The m4 code I've written to check for the script looks like this:

dnl
dnl CGICC_CHECK_CONFIG([PREFIX])
dnl
dnl Check for the configuration script 'cgicc-config' in PATH.  Define
dnl  the macros cgicc_libdir and cgicc_includedir to the values
dnl  obtained from 'cgicc-config'.
dnl
AC_DEFUN(CGICC_CHECK_CONFIG, [
  AC_PATH_PROG(CGICC_CONFIG, cgicc-config, no, [$1/bin:$PATH])
  if test "$CGICC_CONFIG" = no; then
    AC_MSG_ERROR(cgicc-config not found in $1/bin:$PATH)
  fi

  cgicc_libdir=`$CGICC_CONFIG --libdir`
  cgicc_includedir=`$CGICC_CONFIG --includedir`

  AC_SUBST(cgicc_libdir)
  AC_SUBST(cgicc_includedir)
])

Any ideas?

-Stephen
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