#!/usr/bin/perl
use strict;
use warnings;

for my $lines (0 .. 4) {
    print "lines=$lines: ";

    print $lines             ? "A " : "  ";
    print $lines%2           ? "B " : "  ";
    print $lines && $lines%2 ? "C " : "  ";
    print $lines>3           ? "D " : "  ";
    print $lines==3          ? "E " : "  ";
    print( ($lines>3 or $lines==3) ? "F " : "  ");
    print( (($lines && $lines%2) or ($lines>3 or $lines==3)) ? "G " : "  ");
    print "\n";
}

##</code><code>##

$ perl t.pl
lines=0:
lines=1: A B C       G
lines=2: A
lines=3: A B C   E F G
lines=4: A     D   F