So, all these years, you've been wondering what the three-dot version of the flip-flop (..) operator was for? Well, here it is! 
my @numbers = ('25', '12', '32','56','45','21','65');
my @needed = ('25','32','45','65');

my %needed_hash = map { $_ => 1 } @needed;

my @result = grep { $needed_hash{$_} ... $needed_hash{$_} } @numbers;

print "@result\n";

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The grep test starts being true when the item is found in the hash, and also stops being true with the same test. But it won't test the stop condition on the same round as the start condition! That's why the three dots. With only two dots, it would have found the stop condition on the same item.

-- Randal L. Schwartz, Perl hacker
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In reply to •Re: comparing values between two arrays by merlyn
in thread comparing values between two arrays by Anonymous Monk

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