Output a variable to screen/file

Hello,

Following is a pl / sql script example. I need to output the variable l_var1 to a file. How can I do that ? (spooling / print / show / print / refcursor??)

Thanx

DECLARE
   l_var1 VARCHAR2(2000);

BEGIN

      l_var1 := 'This line must be in my file';
     print l_var1;