In LUA scripts you can use the LUA math (including from the math module).  So modulo is simple in LUA,  e.g., "%".
 
But how to do stuff like that in simple slang rules ?
 
 
Absolute Value
 
Code:

iff([Base] < 0,0 - [Base],[Base]) 

 
 
 
MODULO:
 
Code:

++::replace((0 + replace((iff([Base] < 0,0 - [Base],[Base]) /7.0),"\d+(?=\.)","") + 0.01) * 7.0,"\.\d+",""):[Base] <> "" 

 
 
 
notes:
 
Condition of [Base] would ignore value when zero, so we use a text compare <> blank
 
This example is modula for 7.  Use 7".0" to force decimal in result, even if 7 % 7.