s   A signed short value. 16 bits = 2 bytes
    S   An unsigned short value.
          (This 'short' is _exactly_ 16 bits, which may differ from
           what a local C compiler calls 'short'.)

    i   A signed integer value.
    I   An unsigned integer value.
          (This 'integer' is _at least_ 32 bits wide.  Its exact
           size depends on what a local C compiler calls 'int',
           and may even be larger than the 'long' described in
           the next item.)
    l   A signed long value.
    L   An unsigned long value.
          (This 'long' is _exactly_ 32 bits, which may differ from
           what a local C compiler calls 'long'.)
    n   A short in "network" (big-endian) order.
    N   A long in "network" (big-endian) order.
    v   A short in "VAX" (little-endian) order.
    V   A long in "VAX" (little-endian) order.
    q   A signed quad (64-bit) value.
    Q   An unsigned quad value.
          (Available only if your system supports 64-bit integer values
           _and_ if Perl has been compiled to support those.
           Causes a fatal error otherwise.)