This is what I have found as the ideal format for redirecting a single page with a Permanent (301) Redirect in WPENGINE.
Source
^/url-path-here/?$
What this does is…
Destination
Put whatever the full final path is here. For best server performance it should be the full URL e.g. https://fewerthanthree.com/destination-url/
This means that if we had ^/how-to-rock/?$
as the rule then accessing
https://example.com/how-to-rock/
or
https://example.com/how-to-rock
Should both redirect to whatever I put in the Destination.
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