There are many things that you could do to make this more readable/maintainabe.

You could avoid having to use the filehandle on all your print statements by using perlfunc:select to make your file.

You can avoid having to explicitly put "\n" on the end of each line by setting local $\="\n" (see perlvar:$OUTPUT_RECORD_SEPERATOR). This can also be achieved using -l (el) on the command line or shebang line.

You could avoid having to use the print keyword on every line by using multiline quotes. Eg.

print 
"this is line 1 $somevar
this is line 2 $someothervar

this is line 4
this is line 5
";
[download]

You could avoid the long block initialising all the individual variables using array slices.

use constant { NODE=>0, TYPE=>1, COMMENT=>2 ...};
my @d;
@d = ( split '\t' )[ 0,2,6,8,10,12,16,18,20,22,24,26 ];

select AUTOCONF;
print "
# Host @d[NODE, TYPE, CHECK, HOST, ALIVE]
define host{\n
use   generic-host
host_name    $d[NODE]
alias  $d[COMMENT]
address $d[IP]
max_check_attempts    10
notification_interval   7
notification_period   24x7
notification_options   d,u,r
}
";
[download]

Here docs or formats might be even better, but the whole thing is screaming out for a template system like Text::Template.