The mailfromd filter script language operates on entities
of two types: numeric and string.
The numeric type is represented internally as a signed long integer. Depending on the machine architecture, its size can vary. For example, on machines with Intel-based CPUs it is 32 bits long.
A string is a string of characters of arbitrary length. Strings can contain any characters except ASCII NUL.
There is also a generic pointer, which is designed to
facilitate certain operations. It appears only in the body
handler. See body handler, for more information about it.