The following is another way. The block receives an array reference. Between the two, slurping is faster 2.023s versus 2.904s for a FASTA file containing 13.7 million lines excluding headers.
use MCE::Flow;
my $input1 = shift @ARGV;
my @lengths;
mce_flow_f {
chunk_size => '2m', max_workers => 'auto',
gather => \@lengths
},
sub {
my ($mce, $chunk_ref, $chunk_id) = @_;
my (@chunk_lengths);
chomp @{ $chunk_ref };
foreach (@{ $chunk_ref }) {
push @chunk_lengths, length $_ unless />/;
}
MCE->gather(@chunk_lengths);
}, $input1;
MCE::Flow::finish;
print scalar @lengths, "\n";