-static char regexp_sep = '!';
-static char *str_strip_prefix = "!%s!!i";
-static char *str_add_prefix = "!^!%s!";
-static char *str_add_suffix = "!([^/])$!$1%s!";
+static const char regexp_sep = '!';
+static const char *str_strip_prefix = "!%s!!i";
+static const char *str_add_prefix = "!^!%s!";
+static const char *str_add_suffix = "!([^/])$!$1%s!";