Thanks for all! It's working now, i just needed to replacing __END__ to __DATA__.

I need to write simple script, which calling functions from two modules (one of it contains perl code and another contains c code), measuares the time of each and if they calculation results are equals printing time differences of calulation. Problem is that when i include module with c code and run main script perl says: "readline() on unopened filehandle DATA at C:/other_perl/Strawberry/perl/site/lib/Inline.pm line 360. Use of uninitialized value $data in substitution (s///) at C:/other_perl/Strawberry/perl/site/lib/In line.pm line 360. Use of uninitialized value $data in split at C:/other_perl/Strawberry/perl/site/lib/Inline.pm line 3 61. No source code in DATA section for Inline 'C' section. at optest.pl line 0. INIT failed--call queue aborted. One or more DATA sections were not processed by Inline." Here is the main script:

use Time::HiRes qw(gettimeofday tv_interval);
use Test::More;
use perl_calc;
use c_calc;

$start_time_c = [ gettimeofday ];
$c_calc = c_calc::calc_pi();
$end_time_c = [ gettimeofday ];
$elapsed_c = tv_interval($start_time,$end_time);

$start_time_perl = [ gettimeofday ];
$perl_calc = perl_calc::calc_pi();
$end_time_perl = [ gettimeofday ];
$elapsed_perl = tv_interval($start_time,$end_time);

$differences = abs($elapsed_perl - $elapsed_c);

if(ok($c_calc == $perl_calc, "Pi number calc"))
{
    print "C computation time = $elapsed_c\n";
    print "Perl computation time = $elapsed_perl\n";
    print "Differences = $differences\n";
}

done_testing;
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Here is module with c code:

package c_calc;
use Inline 'C';

1;
__END__

__C__
double my_abs(double num)
{
    return (num > 0)? num : -num;
}

double calc_pi()
{
    double real_pi = 3.14159265358979;
    double my_pi = 0;
    double step_sign = 1;
    unsigned long long i = 1;
    while(my_abs(real_pi - my_pi) > 0.00000001)
    {
        my_pi += 4.0/i * step_sign;
        step_sign *= -1;
        i += 2;
    }
    return my_pi;
}
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I read Inline::C-Cookbook, but i didn't find an answer there. So what i do wrong?