while( $xfactor > 0 ){
    my $newfile = sprintf 'new-x-%d-%d', $xfactor, $nimblefoot;
    MahFourThousand( $newfile, $xfactor, $nimblefoot );
    $xfactor--;
}

sub MahFourThousand {
    my $counter = 0;
    while( $counter < 4000 ){
        ## print one line
    $counter++;
    
        ## print 10 lines
        $counter += 10;
    ...
    }
}