It's really quite simple - for and foreach are the same. When you don't care about the value of the current index, don't use it: 
@array = ('a'..'z');
print $_,$/ for @array;

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When you do care about the value of the current index, do use it: 
printf "%02d: %s\n", $_+1, $array[$_] for 0..$#array;

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When in doubt, check with Deparse.pm: 
$ perl -MO=Deparse foo.pl
@array = ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 
'w', 'x', 'y', 'z');
foreach $_ (@array) {
    print $_, $/;
}
foreach $_ (0 .. $#array) {
    printf "%02d: %s\n", $_ + 1, $array[$_];
}
foo.pl syntax OK

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jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

In reply to (jeffa) 5Re: grep, map vs. foreach performance by jeffa
in thread grep, map vs. foreach performance by Anonymous Monk

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