use StringBuffer;
use PerlIO::Tied;
# Note: never close one of the three standard handles. It's almost always a bad idea.
open OLDSTDOUT, ">&=STDOUT";
open STDOUT, ">:tied(StringBuffer)"; # I presume extra arguments to tie get passed as extra argument to open
print STDOUT "this magically gets put to \$stdout\n";
open STDOUT, ">&=OLDSTDOUT";
print STDOUT "this gets put to the original standard output again\n";