#!/usr/bin/perl

# I know there should be
# use strict;
# and
# use warnings;

sub process {
    my ($fileName) = @_;
    open FILE, $fileName or die $!;

    while (<FILE>) {
        chomp $_;
        my @parts = split(',', $_);
        for (@parts) {
          # Do some stuff
        }
    }
}

sub finalize {
    print "Finished\n";
}

my $runlvl = $ARGV[0];

if ($runlvl == 1) {
  # Do everything
  $runlvl = "23";
}

die "Invalid arguments"
  unless ($runlvl =~ /^\d+$/);

# For conversations sake, lets just read this script
my $filename = $0;

print "Run level: $runlvl\n";

# Do some stuff based on the runlevel
for ($runlvl) {
  /2/ and process($filename);
  /3/ and finalize();
}

print "Run level: $runlvl\n";