DB<119> $a=0
 => 0

  DB<120> while ($a++,$a<5) {print "$a\n"}
1
2
3
4

##</code><code>##

  DB<108> use warnings; ("a","b")
 => ("a", "b")

  DB<109> use warnings; scalar ("a","b")
Useless use of a constant (a) in void context at (eval 34)[multi_perl5db.pl:2279] line 1.

##</code><code>##

  DB<135> sub ctx {print wantarray ? 'list' : defined wantarray ? 'scalar' : 'void'; return}

  DB<136> @a= do {ctx();ctx()}   # list-do
voidlist
  DB<137> do {ctx();ctx()};1     # void-do
voidvoid
  DB<138> $a=do {ctx();ctx()}    # scalar-do
voidscalar

  DB<140> scalar (ctx(),ctx())   # scalar comma
voidscalar
  DB<141> 1 while (ctx(),ctx())  # scalar (boolean) comma
voidscalar