Perl 5.10 on CentOS 5

When you call system() with more than one arg, you are telling perl to pass it directly to one of the exec*() calls, so it will not be called with a shell. The shell is the thing that understands file redirection. Try this:

system("wget $url -Omy_folder/$date-$target.html --user-agent=$useragent >/dev/null 2>&1");

Note that this is technically less secure than passing it straight to exec.

For quoting use String::ShellQuote, or just implement the logic yourself:

sub sq {
  my $str = shift;

  if (!$str) {
    $str = "''";
  } else {
    $str =~ s|'|'\\''|g;
    $str = "'$str'";
    $str =~ s|^''||;
    $str =~ s|''$||;
  }

  return($str);
}

$useragent = sq($useragent);
system("wget $url -Omy_folder/$date-$target.html --user-agent=$useragent >/dev/null 2>&1");

Also, to make this a little more sys-admin-y and a little less programmer-y, have you considered using the -q option to wget instead of jumping through the shell/file redirection hoops?

CentOS follow RHEL (Red Hat Enterprise Linux). RHEL 6 is on the way, which means that CentOS 6 will also be released in a few weeks (estimate).

I took a quick look at RHEL 6 repodata, and it seems that Perl will, in the new version, have version 5.10.1:

ftp://ftp.redhat.com/pub/redhat/rhel/beta/6/i386/os/Packages/ perl-5.10.1-106.el6.i686.rpm

Answer: Yes, you can expect it to be available in CentOS in a little while.