This script cleans out old kernels on Ubuntu.

clean-kernels.pl

#!/usr/bin/perl -w

use strict;

my $kernel_version = `uname -r`;
my @kernel = (0,0,0,0);

if($kernel_version =~ /((\d+).(\d+).(\d+)-(\d+))/) {
        $kernel_version = $1;
        $kernel[0] = $2;
        $kernel[1] = $3;
        $kernel[2] = $4;
        $kernel[3] = $5;
}

# This value is used for comparison later on
my $k = sprintf("%04d%04d%04d%04d", @kernel);

my $tmp = join(".", @kernel);
print "Kernel Version: $kernel_version ($tmp)\n";

my $raw_output = `dpkg -l linux-* | grep '^ii' | awk '{print \$2}'`;
my @package_list = split("\n", $raw_output);

my @remove = ();

foreach my $package(@package_list) {
        if($package =~ /(linux-([a-z]*-)+((\d+).(\d+).(\d+)-(\d+)).*)/) {
                my $package_name = $1;
                my $package_version = $3;
                my @version = (0,0,0,0);
                $version[0] = $4;
                $version[1] = $5;
                $version[2] = $6;
                $version[3] = $7;

                my $v = sprintf("%04d%04d%04d%04d", @version);
                if ($v < $k) {
                        $tmp = join(".", @version);
                        print "Removing Package: $package_name\tVersion: $package_version ($tmp)\n";
                        push @remove, $package_name;
                }
        }
}

print "\n";
my $cmd = "sudo apt-get -y remove " . join(" ", @remove);
print $cmd, "\n";

exec $cmd