getting error in fast formula

i have made fast formula and passing parameter to value set its giving me error wrong data type

INPUTS ARE DATA_ELEMENTS (TEXT_TEXT)

l_default_date = TO_DATE('1900/01/01','YYYY/MM/DD')

l_person_id = to_char(GET_CONTEXT(PERSON_ID,0))

IF (DATA_ELEMENTS.EXISTS('Absence_Start_Date')) THEN

(

l_absence_start_date = trunc(TO_DATE(substr(DATA_ELEMENTS['Absence_Start_Date'], 1,10), 'YYYY/MM/DD'))

)

RULE_VALUE = GET_VALUE_SET('GET_ABSNECE_TYPE_VS', '|=PERSON_ID='''||l_person_id||''''||'|Absence_Start_Date='''||l_absence_start_date||'''')

return RULE_VALUE