somecommand 2>&1 | tee logfile
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update: I realized this answer is a bit terse and doesn't really answer the question. If you are actually looking for how to do it in perl, you will have to intercept output from the scripts (send that both to a file and to STDOUT), and the user's input, which will have to be passed along to the script. This can get tricky, expecially if your program doesn't know what should happen next (should it look for output from the script you just ran, or input from the user next?), but IPC::open2/open3 or Expect.pm can do what you want.

Short Description:
------------------
- open a pipe to each given process (@ARGV) 8|
- poll each pipe for new data (optionally print data)
- finished if each filehandle returns eof

#!/usr/local/bin/perl -w

use strict;
use IO::File;

my $count = 0;
my @fdesc = ();
my %fdname;

# create pipes
foreach my $prog (@ARGV) {
  my $fh = IO::File->new("$prog |");
  push(@fdesc, $fh);
  $fdname{$fh} = $prog;
}

# listen
my $notDone=0;
do {
  $notDone=0;
  foreach my $fh (@fdesc) {
    if (!$fh->eof()) {
      $notDone=1;
      print "<",$fdname{$fh},">: ",$fh->getline();
    }
  }
} while ($notDone);
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MP