sub readNLines {
    my $lines_to_read = shift or die '....';
    my @lines_read;
    while(<>) {
        push( @lines_read, $_ );
        last if @lines_read == $lines_to_read;
    }
    if ( @lines_read != $lines_to_read ) {
        # error condition
    }
    return @lines_read;
}

while (@lines = readNLines(4)) { do_stuff() }
[download]

I might even consider the question "What am I reading from the file?" - if it is a record, then I might instead change readNLines to readRecord (as well as the surrounding usage of the data). Then the concept is abstract, and if the format of a record changes, you modify the reading piece. In my opinion,

    while ( my $record = readRecord( ... ) ) { ... }
[download]

    while ( $line1=<> && $line2=<> && $line3=<>... ) { ... }
[download]

Just my $0.02.