Update environment variable Post Processing Tool (Bean Shell Tool)

I want to execute a delete sql as well as an increment an environment variable, I am to fetch the variable  it but dont know the syntax on how to update it ?

public Object execute(AppDefinition appDef, HttpServletRequest request) {
Connection con = null;
try {

DataSource ds = (DataSource)AppUtil.getApplicationContext().getBean("setupDataSource");
con = ds.getConnection();
FormDataDao formDataDao = (FormDataDao) AppUtil.getApplicationContext().getBean("formDataDao");
String envVar1= "#envVariable.cl_id#";

String testSql = "delete from app_fd_r_info where id LIKE '%,%' ";
stmtTest = con.prepareStatement(testSql);
stmtTest.executeUpdate();

}catch(Exception e) {
LogUtil.error("Sample app - Form 1", e, "Error loading user data in load binder");
} finally {
//always close the connection after used
try { if(con != null) {con.close();} } catch(SQLException e) {/* ignored */}
}
return null;
}
//call execute method with injected variable