This isn't about constantness of $errorcount, it is about $errorcount's scope. To make the scope of $errorcount extend to the whole code, declare it before the first unless block.

  my $errorcount = 0;
  unless ($title) {
  ...
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The variable name 'errorcount' also suggests, that you want to count how may errors there are. Currently, each unless block sets the errorcount to 1, disregarding how many errors where counted in prior unless blocks. So within the unless blocks, you want to change the assignment to $errorcount such that it acts as a counter:

# $errorcount = 1;  # probably not what you want
                    # better:
  $errorcount = $errorcount + 1;   # or
  $errorcount += 1;                # or
  $errorcount++;
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