This is not easy stuff. Recipe 16.10 from the Perl Cookbook recommends using IPC::Open3, which brings fork into the picture. Here is Example 16.2 reprinted (i threw in a few minor adjustments). You should be able to wrap this in a sub and pass in the shell command, but please do RTFM the module docs before you just add this to production code, if any.

# cmd3sel - control all three of kids in, out, and error.
use IPC::Open3;
use IO::Select;

my $cmd = "grep vt33 /none/such - /etc/termcap";
my $pid = open3(*CMD_IN, *CMD_OUT, *CMD_ERR, $cmd);

$SIG{CHLD} = sub {
   warn "REAPER: status $? on $pid\n" if waitpid($pid, 0) > 0
};

print CMD_IN "This line has a vt33 lurking in it\n";
close(CMD_IN);

my $selector = IO::Select->new();
$selector->add(*CMD_ERR, *CMD_OUT);

while (my @ready = $selector->can_read) {
   foreach my $fh (@ready) {
      if (fileno($fh) == fileno(CMD_ERR))
         {print "STDERR: ", scalar <CMD_ERR>}
      else                                
         {print "STDOUT: ", scalar <CMD_OUT>}

      $selector->remove($fh) if eof($fh);
   }
}
close(CMD_OUT);
close(CMD_ERR);
[download]

UPDATE: have you looked into Expect?

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)