Ok, I did not know that there exist different versions of how to compute a CRC32. But unfortunately I need this specific one.

Thank you very much for the hint with the Math::BigInt. Now I could get rid of the warnings.

Here the new code:

#!/usr/bin/perl

use strict;
use warnings;

use Math::BigInt;

# solution: 990644297
my $buffer = "/etc/test2.sh";
my $crc = Math::BigInt->new('0');

&determineCrc32($buffer, $crc);

print $crc . "\n";

sub determineCrc32()
{
    my $buffer = $_[0];
    my $crc = $_[1];
    my $i = 0;
    my $val = 0;
    my $k = 0;
    
    for( $i = 0; $i < int(length($buffer) / 4); $i = $i + 1 )
    {
        $val =
            sprintf("%02X", ord(substr($buffer, ($i*4) + 0, 1))) .
            sprintf("%02X", ord(substr($buffer, ($i*4) + 1, 1))) .
            sprintf("%02X", ord(substr($buffer, ($i*4) + 2, 1))) .
            sprintf("%02X", ord(substr($buffer, ($i*4) + 3, 1)));
        
        $crc->badd(hex($val));
        $crc->bmod('0x100000000');
    }

    $val = "";
    $k = 0;
    for( 1 .. int(length($buffer) % 4) )
    {    
        $val .= sprintf("%02X", ord(substr($buffer, ($i*4) + $k, 1)));
        $k++;
    }

    # pad other bytes of 32bit with "00"
    for( 1 .. (4 - int(length($buffer) % 4)) )
    {
        $val .= "00";
    }

    $crc->badd(hex($val));
    $crc->bmod('0x100000000');
}
[download]

Would be very interesting for me how a good perl programmer would code this specific CRC. Because I don't think that my solution is a good way to solve it.

Greetings

My god no! Just replace

% 0x100000000
[download]

with

% (2**32)
[download]

use strict;

# solution: 990644297
my $buffer = "/etc/test2.sh";
my $crc = 0;

for (grep $_, split /(.{1,4})/, $buffer) {
  my $val = sprintf "%02X"x4, map { ord } split //, $_;
  $crc += hex($val);
  $crc %= 2**32;
}

print $crc,$/;
[download]

/(.{1,4})/
should be
/(.{1,4})/s

grep $_, split /(.{1,4})/s, $buffer
is buggy. Fix:
$buffer =~ /(.{1,4})/sg
So much simpler too!

hex sprintf "%02X"x4, map { ord } split //, $_
can be simplified to
unpack 'N', "$_\0\0\0"
The latter should be much faster too.