Here's a method which doesn't use anything but basic arithmetics. It works, but I consider it pretty much unusable due to speed-(or rather lack thereof)-considerations:

sub round {
    my $temp=$_[0];
    my $rounded=0;
    while ($temp>.5) {
          $temp--;
          $rounded++;
    }
    return $rounded;
}

print &round(23.9);
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