Trouble with ARRAYs

There seems to be inadequate info on filling arrays from a table, (vs
keyboarding), and
how to do a lookup in an array. I've tried to almost no avail.

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I have a loop that I'm executing thousands of times and inside of it I have

SELECT INTO myvar column1 FROM mytable WHERE column2 =
somevalue ;

I'm trying to use an array lookup, ala this, that I found in the manual

ANY/SOME (array)
expression operator ANY (array expression)

But I'm a newbie to arrays, so I've tried

DECLARE myarray VARCHAR[] := array['''',''''] ;
then in the body
SELECT INTO myarray ARRAY[column1, column2] from mytable ;

I've discovered via trial and error that the above arrayification works
on a simple SQL query without variables.

How can I go about getting a simple variable out of that array on a
match on another column?

This query executing thousands of times is killing me!

Thanks,
Ralph