Legal label characters

Hi.
Actually "." is valid symbol even at the begining of the label, only it have a little bit special meaning. Point as first char in label defines so called "local" labels. Actually this means that the label with point will be concatenated with the last used "global" label (i.e. without "." as first char) for form the full name of the label. This allows programmer to create equal names for labels in different parts of code, for example subroutines.
Another case is with labels begining with two points: '..'
Such labels are global, but they did not become "current" global label. Example:

Code:

SomeGlobal1:
    nop
.local1: 
    nop
.local2:
SomeGlobal2:
    nop
.local1: 
    nop
..GlobalNotCurrent:
    nop
.local2:
    ret

In the above example the full names of the labels are:
1) SomeGlobal1
2) SomeGlobal1.local1
3) SomeGlobal1.local2
4) SomeGlobal2
5) SomeGlobal2.local1
6) ..GlobalNotCurrent
7) SomeGlobal2.local2

Regards