seek(STDOUT, -0, 2) or die $!;
print STDOUT "abc\n";

##</code><code>##

$ cat a.pl
use Devel::Peek;

open(SAVOUT, '>&STDOUT') or die $!;
close(STDOUT) if $ARGV[0];
open(STDOUT, '+>', "/tmp/stdout.log") or die $!;

Dump(*STDOUT{IO});

@argv = qw(/bin/echo hello world);
system(@argv);

print SAVOUT "before=", tell(STDOUT), "\n";
seek(STDOUT, 0, 0) or die $!;
print SAVOUT "after=", tell(STDOUT), "\n";
while (1) {
  my $rv = read STDOUT, $_, 8192;
  die $! if !defined($rv);
  last unless $_;
  print SAVOUT "stdout=", $_;
}
print SAVOUT "at end=", tell(STDOUT), "\n";
close STDOUT;

$ diff -u <(strace perl a.pl 0 2>&1) <(strace perl a.pl 1 2>&1) | less
...
 lseek(1, 0, SEEK_SET)                   = 0
 lseek(1, 0, SEEK_CUR)                   = 0
-[ code to read locale-dependent version of error message]
-write(2, "Bad file descriptor at a.pl line"..., 37Bad file descriptor at a.pl line 17.
-) = 37
+read(1, "hello world\n", 4096)          = 12
+read(1, "", 4096)                       = 0
+close(1)                                = 0
-write(3, "before=0\nafter=0\n", 17before=0
+write(3, "before=0\nafter=0\nstdout=hello wo"..., 46before=0
 after=0
-)     = 17
+stdout=hello world
+at end=12
+) = 46
 close(3)                                = 0
-exit_group(9)                           = ?
-Process 4028 detached
+exit_group(0)                           = ?
+Process 4032 detached