my @lines;
while (<>) {
    push @lines, $_;
    next if $. % 3;
    ...
    @lines = ();
}

die if @lines;

[download]
can also be written as 
while (!eof()) {
    my @lines;
    defined( $lines[@lines] = <> ) or die for 1..3;
    ...
}

[download]

In reply to Re^2: input record separator by ikegami
in thread input record separator by Anonymous Monk

Title:
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