in reply to Fastest way to grep multiple time on some array

From the description, it sounds like you're taking a big array and trying to split it into a number of smaller arrays. I'd have expected the most efficient approach to be to do everything in a single pass, rather than looping over the array several times.

That is to say, instead of

my @As = grep { /A/ } @bigarray;
my @Bs = grep { /B/ } @bigarray;
my @Cs = grep { /C/ } @bigarray;

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I would write

my (@As, @Bs, @Cs);
for my $item (@bigarray) {
    if    ($item =~ /A/) { push @As, $item }
    elsif ($item =~ /B/) { push @Bs, $item }
    elsif ($item =~ /C/) { push @Cs, $item }
}

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Re^2: Fastest way to grep multiple time on some array
by holli (Abbot) on Feb 19, 2009 at 11:03 UTC
    or even 
    my %H;
for my $item (@bigarray) {
    push @{$H{$1}}, $item
        if ($item =~ /(A|B|C)/);
}

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    holli

    When you're up to your ass in alligators, it's difficult to remember that your original purpose was to drain the swamp.
[reply]
[d/l]
      I think this would fail if one of the items in bigarray was "AB", as it would only add this item to $H{"A"} and not $H{"B"}.

      Alas we don't know for sure whether this would be a problem for the OP or not, but re-reading the post suggests maybe not.

      --
      use JAPH;
      print JAPH::asString();

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