sub popfileb {
    my $countgen0 = 0;
    foreach my $dlp ( 0 .. $LST - 1 ) {
        foreach my $yb ( $dr0[$dlp] .. $dr1[$dlp] ) {
            my $countgen = $countgen0++ - $dr3[$dlp];
            my $change   = $countgen * $dr4[$dlp];
            my $incrs    = int( $dr2[$dlp] + $change );
            my $incrsdel = int( $dr5[$dlp] + abs $change );
            my $chntot   = $incrsdel + $incrs;
            
            foreach my $xb ( 0 .. $total ) {
                
                #set first row;
                if ( $yb == 0 ) {
                    if ( $xb < $dr2[$dlp] ) {
                        substr $aod[0], $xb, 1, 'a';
                    }
                    else {
                        substr $aod[0], $xb, 1, 'n';
                    }
                }
                
                #set increasing rows;
                elsif ( $dr4[$dlp] >= 0 ) {
                    if ( $xb < $dr5[$dlp] + $incrs ) {
                        if ( substr( $aod[ $yb - 1 ], $xb, 1 ) eq 'd' 
+) {
                            substr $aod[$yb], $xb, 1, 'd';
                        }
                        else {
                            substr $aod[$yb], $xb, 1, 'a';
                        }
                    }
                    else {
                        substr $aod[$yb], $xb, 1, 'n';
                    }
                }

                #set decreasing rows;
                else {
                    if ( $xb <= $chntot ) {
                        if ( substr( $aod[ $yb - 1 ], $xb, 1 ) eq 'd' 
+) {
                            substr $aod[$yb], $xb, 1, 'd';
                        }
                        elsif ( substr( $aod[ $yb - 1 ], $xb, 1 ) eq '
+a' ) {
                            substr $aod[$yb], $xb, 1, 'a';
                        }
                        else {
                            substr $aod[$yb], $xb, 1, 'n';
                        }
                    }
                    else {
                        substr $aod[$yb], $xb, 1, 'n';
                    }
                }
            }

            #set random decreased cell;
            if ( $dr4[$dlp] < 0 ) {

                #pre-populate deletion array;
                my @delarray = ( 0 .. $chntot );
                fisher_yates_shuffle( \@delarray );

                my $cndiea = 0;
                foreach my $del ( 0 .. $chntot ) {
                    if ( defined substr( $aod[$yb], $del, 1 )
                        && substr( $aod[$yb], $del, 1 ) eq 'd' )
                    {
                        $cndiea++;
                    }
                }
                my $cnr = $cndiea;
                for my $xd ( 0 .. $chntot ) {
                    my $xda = $delarray[$xd];
                    if (   defined substr( $aod[$yb], $xda, 1 )
                        && substr( $aod[$yb], $xda, 1 ) eq 'a'
                        && $cnr < $incrsdel )
                    {
                        substr $aod[$yb], $xda, 1, 'd';

                        $cnr++;
                    }
                }
            }
        }
    }
    return;
}
[download]