use strict;
use warnings;

my $out ;
{ local  *STDOUT ;
  local  *STDERR ;
  open   STDOUT, '>>', \$out or die "Can't open STDOUT: $!"; # line 28
  open   STDERR, '>>', \$out or die "Can't open STDERR $!"; # line 29
  select STDOUT; $| = 1;  # make unbuffered
  select STDERR; $| = 1;  # make unbuffered
  print "message1\n" ;
  warn  "error1\n"   ;
  print "message2\n" ;
}
print "Result: $out \n" ;

##</code><code>##

Use of uninitialized value in open at ./t2.pl line 29.
Result: message1
error1
message2

##</code><code>##

use CGI qw(:standard append add_parameter);
use strict ;
use warnings ;

print CGI::header() ;

my $out ;

{ local *STDOUT ;
  local *STDERR ;
  open (STDOUT,">>", \$out) ;
  open (STDERR,">>", \$out) ;
  select STDOUT; $| = 1;  # make unbuffered
  select STDERR; $| = 1;  # make unbuffered
  print "message1\n" ;
  warn "error1\n";
  print "message2\n" ;
}
print "Result: $out\n";

##</code><code>##

$ ./t2.pl
Content-Type: text/html; charset=ISO-8859-1

Use of uninitialized value in open at ./t2.pl line 29.
Result: message1
error1
message2