Here's another approach.

{
  #  Arguments to this function are in the order Pre, 
  #  Amble, and Post. Not sure why we're doing a modulo
  #  100 operation here unless it's a substitution for
  #  the int() operator.

  my $Sum = 0;
  my @Values = map { $_ % 100, $Sum += $_, $_; } @_;

  if ( $Sum > 100 )
  {
    #  "If the sum is greater than 100 I wish to favour
    #  amble, then pre, then post."

    my @Index = ( 1, 0, 2 );
    my $ThisElement = 0;

    #  Reduce values in selected order by brute force.
    #  This could be done by calculation instead.

    while ( $Sum > 100 )
    {
      $Values[ $Index[ $ThisElement++ % 3 ] ]--;
      $Sum--;
    }
  }
  elsif ( $Sum < 100 )
  {
    #  "If the sum is less than 100, post takes up the
    #  slack;"

    $Values[ 2 ] -= 100 - $Sum;
  }

  #  In all cases, return the variables, modified or not.

  return ( @Values );
}
[download]

Code is not tested.

--t. alex

"Nyahhh (munch, munch) What's up, Doc?" --Bugs Bunny