Oracle Database Discussions

I'm trying to insert a record into a table, changing the value of the field in the insert based on a condition. To simplify the code:

DECLARE

  true_or_false BOOLEAN;

BEGIN

  true_or_false := FALSE;
      
  INSERT INTO table1
  (column1)
  VALUES
  (CASE WHEN true_or_false = FALSE THEN 0 ELSE -1 END);
  
END;

This is something I can do in SQL Server but can't quite get the Oracle syntax right. Can anyone help me please?