diff -p -u -r automake/ChangeLog automake_patch1/ChangeLog
--- automake/ChangeLog	Mon Aug 13 10:36:40 2001
+++ automake_patch1/ChangeLog	Thu Aug 16 20:59:00 2001
@@ -1,3 +1,15 @@
+2001-08-16  Richard Boulton <address@hidden>
+
+	* automake.in (extract_variable_reference): New function,
+	containing functionality which was previously repeated several
+	times.
+	(define_objects_from_sources): Updated to use
+	extract_variable_reference(), and some comments added.
+	(variable_conditions_recursive_sub): Updated to use
+	extract_variable_reference().
+	(value_to_list): Updated to use extract_variable_reference().
+	(variable_conditions): Badly formatted comment fixed.
+
 2001-08-13  Richard Boulton <address@hidden>
 
 	* automake.in (handle_source_transform): Call
diff -p -u -r automake/automake.in automake_patch1/automake.in
--- automake/automake.in	Mon Aug 13 10:36:40 2001
+++ automake_patch1/automake.in	Thu Aug 16 20:59:00 2001
@@ -665,6 +665,7 @@ my %substnums = ();
 sub register_language (%);
 sub file_contents_internal ($$%);
 sub define_objects_from_sources ($$$$$$$);
+sub variable_conditionally_defined_sub ($$);
 
 
 # &initialize_per_input ()
@@ -2032,6 +2033,53 @@ sub handle_single_transform_list ($$$$@)
     return @result;
 }
 
+# ($ISVAR, $VARNAME, $FROM, $TO)
+# extract_variable_reference ($INPUT)
+# -----------------------------------
+# Extract a variable reference from the input string.
+# Variable references in the forms $(name), ${name}, $(name:from=to) or
+# ${name:from=to} are recognised and decomposed into the variable name, the
+# "from" part of any substitution, and the "to" part of any substitution.
+#
+# Arguments:
+#   $INPUT   The input string, which may or may not contain a variable
+#            reference.
+# Returns:
+#   $ISVAR   Whether a variable was found in $INPUT.
+#   $VARNAME The name of the variable.  Undefined if variable name was a 
+#            @...@ substitution.
+#   $FROM    The from part of the substitution.  Undefined if no substitution.
+#   $TO      The to part of the substitution.  Undefined if no substitution.
+#
+sub extract_variable_reference ($)
+{
+    my ($input) = @_;
+    my ($varname, $from, $to);
+    if ($input =~ /^\$\{([^}]*)\}$/ || $input =~ /^\$\(([^)]*)\)$/)
+    {
+	$varname = $1;
+
+	# If the user uses a losing variable name, just ignore it.
+	# This isn't ideal, but people have requested it.
+	if ($varname =~ /address@hidden@/)
+	{
+	    return ('true', undef, undef, undef);
+	}
+
+	# See if the variable is actually a substitution reference
+	if ($varname =~ /$SUBST_REF_PATTERN/o)
+	{
+	    $varname = $1;
+	    $to = $3;
+	    # Quote non-word characters in from.
+	    ($from = $2) =~ s/(\W)/\\$1/g;
+	}
+
+	return ('true', $varname, $from, $to);
+    }
+    return ('');
+}
+
 # $BOOL
 # define_objects_from_sources ($VAR, $OBJVAR, $NODEFINE, $ONE_FILE,
 #                              $OBJ, $PARENT, $TOPPARENT)
@@ -2074,27 +2122,19 @@ sub define_objects_from_sources ($$$$$$$
 	my @result;
 	foreach my $val (&variable_value_as_list ($var, $cond, $parent))
 	{
-	    if ($val =~ /^\$\{([^}]*)\}$/ || $val =~ /^\$\(([^)]*)\)$/)
+	    my ($isvar, $subvar, $from, $to) = extract_variable_reference($val);
+	    if ($isvar)
 	    {
 		# Handle a sub variable
-		my $subvar = $1;
 
-		# If the user uses a losing variable name, just ignore it.
-		# This isn't ideal, but people have requested it.
-		next if ($subvar =~ /address@hidden@/);
+		# Check if value is to be ignored
+		next if ! defined $subvar;
 
-		# See if the variable is actually a substitution reference
-		my ($from, $to);
-		my @temp_list;
-		if ($subvar =~ /$SUBST_REF_PATTERN/o)
-		{   
-		    $subvar = $1;
-		    $to = $3;
-		    ($from = $2) =~ s/(\W)/\\$1/g;
-		}
+		# Add substitutions to stack
 		push @substfroms, $from;
 		push @substtos, $to;
 
+		# Get name for object variable
 		my $subobjvar = &subobjname($subvar);
 		push (@result, '$('. $subobjvar . ')');
 
@@ -6001,7 +6041,7 @@ sub variable_conditions_recursive ($)
 
 # @CONDS
 # variable_conditions ($VAR)
-# ---------------------------------------
+# --------------------------
 # Get the list of conditions that a variable is defined with, without
 # recursing through the conditions of any subvariables.
 # Argument is $VAR: the variable to get the conditions of.
@@ -6061,19 +6101,15 @@ sub variable_conditions_recursive_sub
 	    last if /^#/;
 
 	    # Handle variable substitutions.
-	    if (/^\$\{(.*)\}$/ || /^\$\((.*)\)$/)
+	    my ($isvar, $subvar) = extract_variable_reference($_);
+	    if ($isvar)
 	    {
-	        my $varname = $1;
-		if ($varname =~ /$SUBST_REF_PATTERN/o)
-		{
-		    $varname = $1;
-		}
- 
+	        next if ! defined $subvar;
 
 		# Here we compute all the conditions under which the
 		# subvariable is defined.  Then we go through and add
 		# $VCOND to each.
-		my @svc = &variable_conditions_recursive_sub ($varname, $var);
+		my @svc = &variable_conditions_recursive_sub ($subvar, $var);
 		foreach my $item (@svc)
 		{
 		    my $val = conditional_string ($vcond, split (' ', $item));
@@ -6277,25 +6313,15 @@ sub value_to_list
 	last if /^#/;
 
 	# Handle variable substitutions.
-	if (/^\$\{([^}]*)\}$/ || /^\$\(([^)]*)\)$/)
+	my ($isvar, $subvar, $from, $to) = extract_variable_reference($_);
+	if ($isvar)
 	{
-	    my $varname = $1;
-
-	    # If the user uses a losing variable name, just ignore it.
-	    # This isn't ideal, but people have requested it.
-	    next if ($varname =~ /address@hidden@/);
-
-	    my ($from, $to);
-	    my @temp_list;
-	    if ($varname =~ /$SUBST_REF_PATTERN/o)
-	    {
-		$varname = $1;
-		$to = $3;
-		($from = $2) =~ s/(\W)/\\$1/g;
-	    }
+	    # Check if value is to be ignored
+	    next if ! defined $subvar;
 
 	    # Find the value.
-	    @temp_list = &variable_value_as_list_recursive_worker ($1, $cond, $var);
+	    my @temp_list;
+	    @temp_list = &variable_value_as_list_recursive_worker ($subvar, $cond, $var);
 
 	    # Now rewrite the value if appropriate.
 	    if (defined $from)