Variable names are not validated

[plinss]

The RFC limits the characters allowed in variables names, but there is no validation enforcing this.

From § 2.3:

 variable-list =  varspec *( "," varspec )
 varspec       =  varname [ modifier-level4 ]
 varname       =  varchar *( ["."] varchar )
 varchar       =  ALPHA / DIGIT / "_" / pct-encoded

(I'm not opposed to expanding the set of allowed characters.)