The $abc identifier will just return the corresponding position or letter of the English alphabet.
Example: $abc(g) ;returns 7 $abc(24) ;returns x $abc(0) ;returns 26 (total letters in alphabet)

The $mod identifier is a simple version of the modulus (%) operator found in many programming and scripting languages. For those not familiar with the modulus operator, it merely takes 2 numbers, divides them and returns the remainder. It's pretty convenient on occasion.
Example: $mod(10,2) ;returns 0 $mod(37,7) ;returns 2

Two simple identifiers. If you have any problems, leave a comment and I'll fix/update with what I can.

abc { 
  var %abc a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.r.s.t.u.v.w.x.y.z r
  return $iif($1 isalpha,$findtok(%abc,$1,46),$iif($1 isnum,$gettok(%abc,$iif($1 == 0,0,$1),46))))
}
mod { var %a = $1, %b = $2, %x = $int($calc(%a / %b)), %y = $calc(%x * %b), %z = $calc(%a - %y) | return %z }