#!/bin/sh

perl -i~ -e '  # -i~ for in-place editing with tilde backup
  use strict;
  use warnings;
  my @a;
  my %excludehash;
  my $file = shift;
  open(excludelist, "< $file") or die;
  chomp( @a=<excludelist> );
  close(excludelist);
  @excludehash{@a}=@a;
  {
    local($/) = "";
    while (<>) {
      m/YOURKEY:\s+(.*)$/m;
      print unless exists $excludehash{ $1 }
    }
  }' "excludefile" "datafile"

##</code><code>##

#!/bin/sh

perl -i~ -e '  # -i~ for in-place editing with tilde backup
  use strict;
  use warnings;
  my %excludehash;
  my $file = shift;
  open(my $excludelist, "<", $file) or die;
  while(<$excludelist>) {
    chomp;
    next if /^$/;
    $excludehash{ $_ }=1;
  }
  close($excludelist);
  {
    local($/) = "";
    while (<>) {
      next if ( m/^YOURKEY:\s+(.*)$/m && $excludehash{ $1 } );
      print
    }
  }' "excludefile" "datafile"

##</code><code>##

1@1
Last, First

##</code><code>##

random lines of data
YOURKEY: 1@1
random lines of data

random lines of data
random lines of data
YOURKEY: 2/
random lines of data

YOURKEY: Last, First
random lines of data
random lines of data

random lines of data
YOURKEY: Apple's

##</code><code>##

#!/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"