sub subroutine {
    my $fh = shift;
    print $fh "Hello, filehandle!\n";
}

my $dest;
open my $fh, '>', \$dest;
subroutine($fh);
close $fh;
print "\$dest is '$dest'";
[download]

That is a cool trick. I looked in opentut and open and didn't see any indication that such a thing was possible. Where did you find out you could do this?

May the Force be with you

If you look about a third of the way down on the "open" man page that you linked to in your own reply, you'll find the part that describes how 'File handles can be opened to "in memory" files held in Perl scalars...'

Stringstreams were introduced somewhere near perl 5.8. Check if you have a new enough perl. If you didn't see this in perlfunc or perlopentut, you might have a too old version.

Darn it, as my kid would say. I guess I didn't really understand that one. Thanks.

So as I understand it, you want to get the string printed by the subroutine into a variable in the calling namespace. If this is what you want try something like this:

use IO::Pipe;
use strict;

my $pipe = IO::Pipe->new();


if(my $pid = fork()){
    waitpid($pid, 0);
    $pipe->reader();
    
    my $str = <$pipe>;

    print "\$str == '$str'\n";
}else{
    $pipe->writer();
    
    &print_to_pipe($pipe);
}


sub print_to_pipe
{
    my $fh = shift;
    print $fh "Hello World\n";
}
[download]

See IO::Pipe.

I just want to get the whole result as a string.

Trying to find out what you mean... Do you want to return the printed string when you call   print? I am a bit puzzled.
The code you write will do what the node's title suggest, print to the filehandle that was passed to the subroutine.

Cheers, Sören