#!/usr/bin/perl -w
use strict;
use feature ':5.10';

my @data=( "abcdefg\n", "hijklmno\n", "pqrstuvw\n", "\n");

my $start_lines;

sub show ($\@) {
        $start_lines or return;
        my ($when,$lines)=($_[0],1+$#{$_[1]});
        my $diff = $start_lines - $lines;
        my $prc = $diff ? 100.0*$diff/$start_lines : 0;
        printf "%10.10s %d -> %d lines or %.2f%% reduction\n",
                $when, $start_lines, $lines, $prc;
}

sub printar(\@) {
        my $ar=$_[0];
        printf "\n(#lines=%d,", 0+@$ar;
        for (my $i=0; $i<=$#$ar; ++$i) {
                printf " line %d: '%s'", $i, $ar->[$i];
        }
        print ")\n";
}

sub uniq(\@) {
        my $ar=$_[0];
        my @res;
        foreach (@{$ar}) {
                my $ans=grep /^$_$/, @res;
                printf "line \"%s\" in ar?: %s, ar: ", 
                        $_ // "undef" , $ans?"yes":"no";
                printar @res;
                if (!$ans) {push @res, $_}
        }
        @res;
}


###   main

#my @msgs=<>;
my @msgs=@data;
$start_lines=@msgs;
show("before", @msgs);

my $msgs=join "", @msgs;
my @deblanked=split /\n/, $msgs;
show "deblanked", @deblanked;

my @uniq=uniq @deblanked;
show "after uniq", @uniq;