open( X, 'x.txt' );
my ( $chunk, $line );
while (<X>) {
    $line = $_;
    if ( ( length($chunk) + length($line) ) > 2048 ) {
        # if the next line would take us over the set size
        doSomethingWithChunk($chunk);
        $chunk = $line;
    }
    else {
        $chunk .= $line;
        # append line and keep going
    }
}
doSomethingWithChunk($chunk);
# process whatever's left in $chunk at the end

##</code><code>##

my $p = new Algorithm::Permute(['a'..'d']);
  while (@res = $p->next) {
    # do something with @res
  }