foreach my $logline (@raw_data) { 
    my $is_already_in_parsed_data = 0; 
 
    PARSED_LOOP: 
    foreach my $line (@parsed_data) { 
        if ( $logline eq $line ) { 
            $is_already_in_parsed_data = 1; 
            last PARSED_LOOP; 
        } 
    } 
 
    if ( not $is_already_in_parsed_data ) { 
        print "Line not seen before: '$logline'\n"; 
        push @parsed_data, $logline; 
    } 
}

my %parsed_data; 
foreach my $logline (@raw_data) { 
    my $is_already_in_parsed_data = exists $parsed_data{$logline}; 
 
    if ( not $is_already_in_parsed_data ) { 
        print "Line not seen before: '$logline'\n"; 
        $parsed_data{$logline}++; 
    } 
}

#!/usr/bin/perl 
use strict; 
use warnings; 
 
=begin comment 
 
2005-10-25  Bruce Gray <bruce.gray@acm.org> 
Wrote program. 
 
This program reads a file, printing the first occurrence of  
each line as it is seen. It dumps a count of the number of  
occurrences of each line into a save file. In subsequent  
runs of the program, the save file is used to initialize the  
count (and therefore the state of whether an occurrence is "first"). 
 
Program written in answer to Perl Guru request: 
  http://perlguru.com/gforum.cgi?post=24449;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;guest= 
 
=cut 
 
 
# Configuration: 
my $data_file = 'c:/demolog.txt'; 
my $save_file = 'c:/savelog.txt'; 
 
# Read any counts of data lines from the save file. 
# Place them in %lines_seen. 
my %lines_seen; 
if ( -s $save_file ) { 
    open SAVE, '<', $save_file 
      or die "Could not open '$save_file': $!"; 
 
    while (<SAVE>) { 
        chomp $_; 
        my ( $count, $data_line ) = split "\t", $_, 2; 
        $lines_seen{$data_line} = $count; 
    } 
 
    close SAVE 
      or warn "Could not close '$save_file': $!"; 
} 
 
 
 
# Read the data file one line at a time, using the existence of 
# the line in %lines_seen to determine if the is a line we have seen. 
# Print new lines. 
open DAT, '<', $data_file 
  or die "Could not open '$data_file': $!"; 
 
while (<DAT>) { 
    chomp $_; 
 
    my $is_new = not exists $lines_seen{$_}; 
 
    if ( $is_new ) { 
        print "Line not seen before: '$_'\n"; 
    } 
 
    $lines_seen{$_}++; 
}  
 
close DAT 
  or warn "Could not close '$data_file': $!"; 
 
 
 
# Overwrite the save file with the updated lines and counts. 
open SAVE, '>', $save_file 
  or die "Could not open '$save_file': $!"; 
 
while ( my ( $data_line, $count ) = each %lines_seen ) { 
    print SAVE "$count\t$data_line\n"; 
} 
 
close SAVE 
  or warn "Could not close '$save_file': $!";