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 ???