app_perl: docs for parse_mode parameter

src/modules/app_perl/doc/app_perl_admin.xml

@@ -235,6 +235,30 @@ modparam("app_perl", "reset_cycles", 100000)
 ...
 modparam("app_perl", "perl_destroy_func", "my_perl_destroy")
 ...
+</programlisting>
+			</example>
+		</section>
+
+		<section id="app_perl.p.parse_mode">
+			<title><varname>parse_mode</varname> (int)</title>
+			<para>
+			Control how to behave on perl_parse() return code - on some versions
+			it is the value for application exit and can break reloading.
+			</para>
+			<para>
+			If set to 0, continue even of perl_parse() returns non-zero, logging
+			a warning. If set to 1, realod fails on non-zero return code and
+			triggers an exit.
+			</para>
+			<para>
+			Default value is <emphasis>0</emphasis>.
+			</para>
+			<example>
+			<title>Set <varname>parse_mode</varname> parameter</title>
+			<programlisting format="linespecific">
+...
+modparam("app_perl", "parse_mode", 1)
+...
 </programlisting>
 			</example>
 		</section>