Here's an approach that initializes a hash of output tokens, prepopulated with marker text for new additions. The output data is overridden for existing entries, and a sorted list is appended to the specified output file (open with '>' instead of '>>' if you don't want this). Note that it isn't fully compatible with the delete code I posted earlier, since that code didn't take comments into account.
#!/usr/local/bin/perl
use strict;
use warnings;
if (@ARGV != 3) {
print "Usage: $0 <pattern file> <input file> <output file>\n";
exit;
}
my ($pattern_filename, $source_filename, $dest_filename) = @ARGV;
open my $pattern_fh, '<', $pattern_filename or die "Failed to open $pa
+ttern_filename: $!";
my %output_tokens = ();
while (my $line = <$pattern_fh>) {
chomp $line;
$output_tokens{$line} = "$line # Added by script";
}
print "Expected tokens: ", join(', ', keys %output_tokens), "\n";
open my $infile, "<", $source_filename or die "Failed to open $source
+_filename: $!";
open my $outfile,">>", $dest_filename or die "Failed to open $dest_f
+ilename: $!";
while(my $line = <$infile>) {
chomp $line;
$output_tokens{$line} = $line;
}
for my $token (sort keys %output_tokens) {
print $output_tokens{$token}, "\n";
}
close($infile);
close($outfile);