This may be a little overblown for what you need, but it will capture both the STDOUT and the STDERR to a log file, die if the program does not exist, and display the return code.

#!/usr/bin/perl

use strict;
use warnings;

use IPC::Run qw( start pump finish );

open(LOG, '>', 'log') or die "Unable to open log: $!";
my ($in, $out);
my $h = start([ 'run_tool', '-f', 'test.tcl' ], \$in, \$out, \$out);
while($h->pump) {
    print LOG $out;
    $out = '';
}
$h->finish;
close(LOG);
print "Exit code was: " . $h->result . "\n";
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You'll probably want to take a closer look at the IPC::Run docs for more details on what all it can do. It also offers fairly flexible control over interactive programs if you want to do that in the future. I tend to use it over open or system any time I need to start doing anything more than just run the program.