Try like:

Map:
Mapping LOAD 
     Trim(SubField(Purgechar([substring's to check], chr(39)), ',')) as Substring,
     '|'&Category&'|'
FROM
[https://community.qlik.com/t5/App-Development/How-to-match-the-list-of-substrings-with-a-field-and-map-the/td-p/2011849]
(html, utf8, UserAgent is 'Mozilla/5.0', embedded labels, table is @2);


t2:	
LOAD Comment,
	 TextBetween( MapSubString('Map',Comment), '|', '|') as MappedCategory
FROM
[https://community.qlik.com/t5/App-Development/How-to-match-the-list-of-substrings-with-a-field-and-map-the/td-p/2011849]
(html, utf8, UserAgent is 'Mozilla/5.0', embedded labels, table is @1);