#!/usr/bin/perl
use constant DAILY_RUN => 1024 * 1024 * 1000;
use strict;
use warnings;

my $file = $ARGV[0] or die "Usage: $0 <input_file>";
open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $!";

my $cnt = 1;
my $out_file = "$file.$cnt";

# Will clobber an existing file by this name (fix if important)
open(my $out_fh, '>', $out_file) or die "Unable to open '$out_file' for writing: $!";

while (<$fh>) {
    if (-s $out_file > DAILY_RUN && /^100/) {
        ++$cnt;
        $out_file = "$file.$cnt";
        open($out_fh, '>', $out_file) or die "Unable to open '$out_file' for writing: $!";
    }
    print $out_fh $_;
}