diff --git a/src/core/settings.c b/src/core/settings.c
index 4e0717cd..881a129e 100644
--- a/src/core/settings.c
+++ b/src/core/settings.c
@@ -703,6 +703,13 @@ int irssi_config_is_changed(const char *fname)
 		 config_last_checksum != file_checksum(fname));
 }
 
+static gboolean filter_stub(const char *key, const char *value, char **new_value)
+{
+	g_warning("Filtering %s in %s", value, key);
+	*new_value = (char *)value;
+	return TRUE;
+}
+
 static CONFIG_REC *parse_configfile(const char *fname)
 {
 	CONFIG_REC *config;
@@ -736,6 +743,8 @@ static CONFIG_REC *parse_configfile(const char *fname)
 		config = config_open(NULL, -1);
 	}
 
+	config_set_filter_function(filter_stub);
+
         if (config->fname != NULL)
 		config_parse(config);
         else
diff --git a/src/lib-config/get.c b/src/lib-config/get.c
index a83686fd..eca12610 100644
--- a/src/lib-config/get.c
+++ b/src/lib-config/get.c
@@ -20,6 +20,8 @@
 
 #include "module.h"
 
+static ConfigFilterFunc filter_func = NULL;
+
 CONFIG_NODE *config_node_find(CONFIG_NODE *node, const char *key)
 {
 	GSList *tmp;
@@ -165,7 +167,7 @@ CONFIG_NODE *config_node_traverse(CONFIG_REC *rec, const char *section, int crea
 char *config_get_str(CONFIG_REC *rec, const char *section, const char *key, const char *def)
 {
 	CONFIG_NODE *parent, *node;
-	char *path;
+	char *path, *value;
 
 	g_return_val_if_fail(rec != NULL, (char *) def);
 	g_return_val_if_fail(key != NULL, (char *) def);
@@ -190,7 +192,18 @@ char *config_get_str(CONFIG_REC *rec, const char *section, const char *key, cons
 		}
 	}
 
-	return (node == NULL || !has_node_value(node)) ? (char *) def : node->value;
+	if (node == NULL || !has_node_value(node))
+	{
+		return (char *)def;
+	}
+
+	if (node->do_filter && filter_func)
+	{
+		return filter_func(key, node->value, &value) ?
+			value : (char *)def;
+	}
+
+	return node->value;
 }
 
 int config_get_int(CONFIG_REC *rec, const char *section, const char *key, int def)
@@ -216,12 +229,24 @@ int config_get_bool(CONFIG_REC *rec, const char *section, const char *key, int d
 char *config_node_get_str(CONFIG_NODE *parent, const char *key, const char *def)
 {
 	CONFIG_NODE *node;
+	char *value;
 
         if (parent == NULL) return (char *) def;
 
 	node = config_node_find(parent, key);
-	return (char *) ((node != NULL && has_node_value(node)) ?
-			 node->value : def);
+
+	if (node == NULL || !has_node_value(node))
+	{
+		return (char *)def;
+	}
+
+	if (node->do_filter && filter_func)
+	{
+		return filter_func(key, node->value, &value) ?
+			value : (char *)def;
+	}
+
+	return node->value;
 }
 
 int config_node_get_int(CONFIG_NODE *parent, const char *key, int def)
@@ -339,3 +364,8 @@ GSList *config_node_next(GSList *list)
 	list = list->next;
         return config_node_first(list);
 }
+
+void config_set_filter_function(ConfigFilterFunc func)
+{
+	filter_func = func;
+}
diff --git a/src/lib-config/iconfig.h b/src/lib-config/iconfig.h
index 9b6e5c1e..9211eb22 100644
--- a/src/lib-config/iconfig.h
+++ b/src/lib-config/iconfig.h
@@ -18,8 +18,9 @@ typedef struct _CONFIG_NODE CONFIG_NODE;
 typedef struct _CONFIG_REC CONFIG_REC;
 
 struct _CONFIG_NODE {
-	int type;
-        char *key;
+	int type      : 8;
+	int do_filter : 1;
+	char *key;
 	void *value;
 };
 
@@ -46,6 +47,10 @@ struct _CONFIG_NODE {
 
 */
 
+typedef gboolean (*ConfigFilterFunc)(const char *key,
+				     const char *value,
+				     char **new_value);
+
 struct _CONFIG_REC {
 	char *fname;
 	int create_mode;
@@ -72,6 +77,8 @@ CONFIG_REC *config_open(const char *fname, int create_mode);
 void config_close(CONFIG_REC *rec);
 /* Change file name of config file */
 void config_change_file_name(CONFIG_REC *rec, const char *fname, int create_mode);
+/* Set the default function to handle the variable filtering */
+void config_set_filter_function(ConfigFilterFunc func);
 
 /* Parse configuration file */
 int config_parse(CONFIG_REC *rec);
diff --git a/src/lib-config/parse.c b/src/lib-config/parse.c
index c106fc46..cbb11163 100644
--- a/src/lib-config/parse.c
+++ b/src/lib-config/parse.c
@@ -131,7 +131,7 @@ static GTokenType config_parse_symbol(CONFIG_REC *rec, CONFIG_NODE *node)
 {
 	CONFIG_NODE *newnode;
 	GTokenType last_char;
-	int print_warning;
+	int print_warning, do_filter;
 	char *key;
 
 	g_return_val_if_fail(rec != NULL, G_TOKEN_ERROR);
@@ -151,12 +151,21 @@ static GTokenType config_parse_symbol(CONFIG_REC *rec, CONFIG_NODE *node)
 		config_parse_get_token(rec->scanner, node);
 	}
 
+	do_filter = FALSE;
+
  	switch (rec->scanner->token) {
+	case '&':
+		/* substitute value */
+		do_filter = TRUE;
+		config_parse_warn_missing(rec, node, G_TOKEN_STRING, TRUE);
+		g_assert(rec->scanner->token == G_TOKEN_STRING);
 	case G_TOKEN_STRING:
 		/* value */
-		config_node_set_str(rec, node, key, rec->scanner->value.v_string);
+		newnode = config_node_set_str(rec, node, key, rec->scanner->value.v_string);
 		g_free_not_null(key);
 
+		newnode->do_filter = do_filter;
+
 		print_warning = TRUE;
 		if (node->type == NODE_TYPE_LIST) {
 			/* if it's last item it doesn't need comma */
@@ -167,7 +176,6 @@ static GTokenType config_parse_symbol(CONFIG_REC *rec, CONFIG_NODE *node)
 
 		config_parse_warn_missing(rec, node, last_char, print_warning);
 		break;
-
 	case '{':
 		/* block */
 		if (key == NULL && node->type != NODE_TYPE_LIST)
diff --git a/src/lib-config/write.c b/src/lib-config/write.c
index 37e51f09..4558e77a 100644
--- a/src/lib-config/write.c
+++ b/src/lib-config/write.c
@@ -142,6 +142,7 @@ static int config_write_node(CONFIG_REC *rec, CONFIG_NODE *node, int line_feeds)
 	case NODE_TYPE_KEY:
 		if (config_write_word(rec, node->key, FALSE) == -1 ||
 		    config_write_str(rec, " = ") == -1 ||
+		    (node->do_filter && config_write_str(rec, "&") == -1) ||
 		    config_write_word(rec, node->value, TRUE) == -1)
 			return -1;
 		break;
@@ -212,6 +213,8 @@ static int config_node_get_length(CONFIG_REC *rec, CONFIG_NODE *node)
 	case NODE_TYPE_KEY:
 		/* "key = value; " */
 		len = 5 + strlen(node->key) + strlen(node->value);
+		/* optional '&' before the value */
+		len += node->do_filter ? 1 : 0;
 		break;
 	case NODE_TYPE_VALUE:
 		/* "value, " */