Function to check space, check first & last characters, check alphabets or numbers, & check between certain alphabets ? SAP DS 4.2

If DEF456 = spaces then 'Not Applicable'

else If first 5 chars of DEF456 are numeric then set to '01' 

Else if (chars 1-2 of DEF456 are numeric and chars 3-4 are (numeric or blank) and  char 5 =' '  ) then set to '02'

Else if (char 1 of DEF456 is in [A-V] and chars 2-5 are numeric then ) then set to '06'

Else if (char 1 of DEF456 is in [W-Z] and chars 2-5 not blank and chars 2-5 are alphnumeric and chars 2-5 contains at least one char and a digit) then set to '06'

else Set the default value of DEF456 as '10'

I am trying to code this in SAP DS 4.2. But I am not sure whats the is_alpha or is_num functions are ?

I found is_valid_date & is_valid_time but not these below:

Function to:

check space = ?

check first & last characters = ?

check alphabets or numbers = ?

check between certain alphabets = ?

Any help would be greatly appreciated !

Thanks