PL/SQL: Check to see if the date is in the format of 'MM/DD/YYYY'

CREATE or REPLACE FUNCTION validate_date_format(p_input_date VARCHAR2)
RETURN BOLEAN IS

l_result_date DATE;

BEGIN

l_result_date := TO_DATE(p_input_date, 'MM/DD/YYYY');

IF LENGTH(SUBSTR(p_input_date, INSTR(p_input_date, '/', 1, 2) + 1)) = 4
THEN

RETURN TRUE;

ELSE

RETURN FALSE;

END IF;

EXCEPTION
WHEN OTHERS then
RETURN FALSE;

END;

PL/SQL: String concatenation

FUNCTION dyna_string1(p_string varchar2) RETURN VARCHAR2 IS

t VARCHAR2(2) :=',';
t1 VARCHAR2(2) :='''';
t2 VARCHAR2(32767);
t_check NUMBER(10);
newstring VARCHAR2(32767);

BEGIN

newstring :=p_string;
t_check :=instr(newstring,',');
IF t_check!=0 THEN
t2 := t1tt1;
newstring := replace(newstring,',',t2);
newstring := '('''''newstring''''')';
ELSE
newstring:=newstring;
newstring:='('''''newstring''''')';
END IF;
RETURN newstring;

END dyna_string1;