#!/usr/bin/perl -T --

use strict;
use warnings;

my $testCase = 'testing';
my $command = 'lin --help';

my $test = sprintf "/usr/anil/scripts/ActData/%s.txt", $testCase;
open (STDERR, ">", $test )
  or die "couldn't create $test : $!";
$t = system($command);
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See perlopentut, perlsec, sprintf