.ig
Create a register, then create an alias to it, then alias the original
name to the alias.  This should work.
..
.cp 0
.nr r1 10 1
Original value of r1: \n[r1]
.br
Increment r1.
.br
.nr r1 \n+[r1]
.aln r2 r1
Value of alias r2: \n[r2]
.br
Increment r2.
.br
.nr r2 \n+[r2]
.aln r1 r2
Value of alias r1: \n[r1]
.br
