#!/bin/sh

perl -i~ -e '
  use strict;
  use warnings;
  my %excludehash;
  {
    local($/) = "";
    {
      while(<>) {
        while (m/^OBSPOR: (.*)$/mg) {
          $excludehash{ $1 } = $1
        }
        last if (eof)
      }
    }
    seek(ARGV, 0, 0);
    {
      while (<>) {
        m/^PORNUM:\s+(.*)$/m;
        print unless exists $excludehash{ $1 }
      }
    }
  }' "datafile"