If you are under any system with the Unix toolset available, the split command already does this and more. If you're bent on using Perl, the Perl Power Tools also have a pure Perl implementation of split.

Personally, I would make the script more flexible by parsing the options via GetOpt::Long and having the input file as the last parameter. Having it as the last parameter allows the script to be used within a shell pipeline like gunzip -c my_file | perl -w partition_file.pl 1000, and it makes the rest of the parameters independent from their position.

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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