I've seen this type of code used in a number of places (and even have it in a few of my own do-files having taken it from other Statalist posts):

Code:
local nb=`.FigureName.plotregion1.barlabels.arrnels'
forval i=1/`nb' {
  .FigureName.plotregion1.barlabels[`i'].text[1]="`.FigureName.plotregion1.barlabels[`i'].text[1]'%"
}
.FigureName.drawgraph
What is this? It seems to allow the user to do things which are undocumented. I have no idea how versatile it is, nor where it's documented. Does anyone know where this kind of thing is documented? I'd love to learn how to use it as needed. If it's not documented, how have people learned it?