The weapon proficiency list file is to set what each weapon category a weapon belongs to (Simple, Martial, Exotic, Natural) so that PCGen can determine whether or not a character qualifies to use that weapon or not. The 1st field is the name field, there is no tag for it, just the name of the weapon proficiency.
Tag Name: HANDS:x
Variables Used (x): Number (Number of hands)
What it does:
#IFLARGERTHANWEAPON
    is a flag that checks if the
characters size is larger than the weapon.
    .MOD
    tag, given an existing
    HANDS
    tag, the data included in
a new
    HANDS
    tag will overwrite the existing tag
data.
   Examples:
   HANDS:2
  
Weapon is wielded with two hands.
   HANDS:1IFLARGERTHANWEAPON
  
Weapon is wielded with one hand if the PC is larger than the weapon size.
.MOD Example:
   Initial Template:
   Ogre Axe <tab>
HANDS:1
  
   Modified By:
   Ogre Axe.MOD <tab>
HANDS:2
  
   Results In:
   Ogre Axe <tab>
HANDS:2
  
Weapon is wielded with two hands.