If you don't already have it, download File::Temp and use it. Really.

With that what you want to do can be done as:

use File::Temp qw(tempfile);

my $temp_fh = tempfile();
my $saved_fh = select($temp_fh);
eval "print 'Waka waka!'";
seek ($temp_fh, 0, 0);
select($saved_fh);
$text = join '', <$temp_fh>;
print "The text was '$text'\n";
[download]

In fact looking at this, you can add error trapping etc while turning this into a function:

use File::Temp;
use Carp;

# Takes code to be evaled, supresses printing and returns
# the text that would have been printed.
sub eval_print_trap {
  my $code = shift;

  my $temp_fh = tempfile();
  my $saved_fh = select($temp_fh);
  eval($code);
  select($saved_fh);

  if ($@) {
    confess("Evaling \n'$code'\ngave error $@");
  }
  seek($temp_fh, 0, 0);
  wantarray ? <$temp_fh>: join '', $temp_fh;
}
[download]

The point being, of course, that the error handling is a Good Thing to add, you now have a piece of reusable functionality which does not assume that STDOUT had been the previous selected default filehandle, and in your code wouldn't you rather see:

my $output = eval_print_trap("print 'Waka waka!'");
[download]

than all of the garbage it required?

Caveat programmer: Perl's select will only redirect prints to the default output from Perl code. You will not trap error output, and you will not trap any printing that comes within C code or other programs. Good luck if you plan to call system.

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