{
   local $_;
   do {
      $_ = <INHANDLE>;
      ...
   } while defined $_;
}

##</code><code>##

for (;;) { # Loop until "last".
   local $_ = <INHANDLE>;
   ...
   last if not defined $_;
}

##</code><code>##

{ # Loop while "redo".
   local $_ = <INHANDLE>;
   ...
   redo if defined $_;
}

##</code><code>##

my $block = sub { ... };
&$block while <INHANDLE>;
&$block foreach undef;

##</code><code>##

for (;;) { # Loop until "last".
   local $_ = <DATA>;

   if (defined) {
      print;
   } else {
      print("[undef]\n");
   }

   last unless defined $_;
}

##</code><code>##

a
b
c
[undef]