SET TERM ^ ;

CREATE OR ALTER PROCEDURE Proc2
RETURNS (
  Text CHAR(31))
AS
BEGIN
  FOR
    SELECT T.Rdb$type_name
      FROM Rdb$types T
      INTO :Text
  DO
    SUSPEND;
END^

CREATE OR ALTER PROCEDURE Proc
RETURNS (
  Text VARCHAR(100))
AS
BEGIN
  -- По F7 заходим
  FOR
    SELECT
           CASE P.Text
              WHEN 'TEXT' THEN P.Text
              ELSE ''
           END
      FROM Proc2 P
      INTO :Text
  DO
    SUSPEND;

  -- По F7 НЕ заходим
  FOR
    SELECT IIF(P.Text = 'TEXT', P.Text, '')
      FROM Proc2 P
      INTO :Text
  DO
    SUSPEND;
END^

SET TERM ; ^

GRANT EXECUTE ON PROCEDURE PROC2 TO PROCEDURE PROC;