wiki.clockworkpi.com/_includes/functions/wiki-pages.html

{%- assign wiki_pages = '' | split: '' -%}
{%- for collection in site.collections -%}
  {%- assign prefix = collection.label | slice: 0, 4 -%}
  {%- if prefix == 'wiki' -%}
	  {%- assign wiki_pages = wiki_pages | concat: collection.docs -%}
  {%- endif -%}
{%- endfor -%}