One-weapon Fighting Feat help

[Mathizsias]

I'm looking for help on my One-weapon fighting feat, on the improved version I want it to add an extra attack onto the sheet, but I can't seem to understand the workings of tAtkMelFlu or any of the extra attacks added mechanism.

The eval currently looks like this and was modified from Two-weapon fighting:

      ~ If we're disabled, do nothing
      doneif (tagis[Helper.FtDisable] <> 0)
      
      ~ Check to see if we have something equipped in off hand
      doneif (hero.tagis[Hero.EquipOff] < 1)
      

      ~ Check to see if our Unarmed Strike is selected in either main or off
      ~ hands
      doneif (hero.child[wUnarmed].tagis[Hero.OffHand] > 1)
      
      ~ Otherwise, add a +1 Shield bonus to our AC
      #applybonus[tACNatural, hero.child[ArmorClass], field[abValue].value]
      
      ~ If we're in output mode, don't do anything
      doneif (state.isoutput <> 0)
      
      #appenddesc[pstTotDef,"{b}Addition from Two-weapon Defense{/b}: When wielding a double weapon or two weapons (not including natural weapons or unarmed strikes), you gain a " & signed(field[abValue].value) & " shield bonus to your AC.{br}{br}When you are fighting defensively or using the total defense action, this shield bonus increases to " & signed(field[abValue2].value) & "."]
      #appenddesc[pstFtDefen,"{b}Addition from Two-weapon Defense{/b}: When wielding a double weapon or two weapons (not including natural weapons or unarmed strikes), you gain a " & signed(field[abValue].value) & " shield bonus to your AC.{br}{br}When you are fighting defensively or using the total defense action, this shield bonus increases to " & signed(field[abValue2].value) & "."]
      
      ~ if we're fighting defensively or total defense, the shield bonus increases to +2
      if (#hascondition[pstFtDefen] + #hascondition[pstTotDef] <> 0) then
        #applybonus[tACNatural, hero.child[ArmorClass], field[abValue2].value]
        endif

I want to add an extra attack with a -3 penalty, much like anyone will eventually get by leveling high enough. For the greater version I made it needs to be an extra attack without penalty.

Thanks for any help, in advance.