how to insert multiple rows and get the ids back in a temp table (pgplsql)?

how can I do the following in plpgsql?
insert multiple rows in a table
get the ids (serial) into a temp table (not the client)

for one row it will be like this
insert into mytable(mycolumn)values(123)returning id into some_variable;

now for multiple rows (using insert select) it will be like

insert into mytable(mycolumn)
select other_column from other_table
returning id into ???