Just do it like this:   (a sketch ... not code-writing services)

First, write your query to use a placeholder:
select foo.id as key,(select value from foo_data where aktivity is true
and foo.id=foo_id and key='name'
order by id desc limit 1) as value
from foo where id!=?

Now, when you’t called $dbh->prepare($sql); with this SQL string to get your statement-handle, $sth, call $dbh->execute('xyzzy';, which, as you can see, provides a @bind_values array as shown in the perldoc.   The first value in the array (in this case, 'xyzzy', will be provided to the database engine so that it will use that value in place of the first placeholder '?' and so-on.   (It doesn’t do a textual substitution ... the SQL string is compiled only once, but it has “an input-variable,” so to speak.   The question-mark is not quoted:   it is not a “literal string.”

You should n-e-v-e-r construct an SQL string yourself, using any input provided by ... well ... anyone.   This is what placeholders are for.   It neatly avoids the Bobby Tables problem.

Notice also that, having prepared the statement-handle, you can execute() it as many times as you want to, providing different bind-parameters each time.   This is efficient, because the SQL engine builds its execution-plan for the query only once, then re-executes it multiple times.