Allow building without Perl

This reverts commit a0c8de3f3f.
cf. https://github.com/tats/w3m/pull/221

configure

@@ -4118,24 +4118,28 @@ else
   RANLIB="$ac_cv_prog_RANLIB"
 fi
 
-# Extract the first word of "perl", so it can be a program name with args.
-set dummy perl; ac_word=$2
+for ac_prog in perl
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 $as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_PERL+:} false; then :
+if ${ac_cv_path_PERL+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  if test -n "$PERL"; then
-  ac_cv_prog_PERL="$PERL" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+  case $PERL in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PERL="$PERL" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_PERL="$(command -v perl)"
+    ac_cv_path_PERL="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -4143,10 +4147,10 @@ done
   done
 IFS=$as_save_IFS
 
-  test -z "$ac_cv_prog_PERL" && ac_cv_prog_PERL="no"
+  ;;
+esac
 fi
-fi
-PERL=$ac_cv_prog_PERL
+PERL=$ac_cv_path_PERL
 if test -n "$PERL"; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PERL" >&5
 $as_echo "$PERL" >&6; }
@@ -4156,7 +4160,10 @@ $as_echo "no" >&6; }
 fi
 
 
-test "$PERL" == "no" && as_fn_error $? "Required program 'perl' not found." "$LINENO" 5
+  test -n "$PERL" && break
+done
+test -n "$PERL" || PERL="/usr/local/bin/perl"
+
 for ac_prog in nkf
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.

configure.ac

@@ -25,8 +25,7 @@ AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
 AC_PROG_RANLIB
-AC_CHECK_PROG(PERL,[perl],[$(command -v perl)],[no])
-test "$PERL" == "no" && AC_MSG_ERROR([Required program 'perl' not found.])
+AC_PATH_PROGS(PERL, perl, /usr/local/bin/perl)
 AC_PATH_PROGS(NKF, nkf, /usr/local/bin/nkf)
 AC_PATH_PROGS(MAN, man, /usr/bin/man)
 AC_PATH_XTRA