Hmm, if you need to keep track of iteration in a loop, then you should use for instead of foreach. 
for (my $i=0; $i < $#array; $i++) {

    #print every third line
    print "$array[$i]\n" if (($i % 3)==0);
    
    #or even more consise
    print "$array[$i]\n" unless ($i%3);
}

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I know that for is a synonym for foreach, but I simply prefer to use a for construct if I am going to need the current iteration. Guess it's the C inside me. Oh, thanks to KM - I'll be more idiomatic next time. ;)

/me seeks Priest to exorcise evil C demons.

In reply to (jeffa) Re: Of foreach loops and counting by jeffa
in thread Of foreach loops and counting by Cirollo

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