my @a = qw( a b c );

for ( my $i=0; $i<3; $i++ ){
    say $a[$i];
}

##</code><code>##

for my $elem ( @a ){
    say $elem;
}

##</code><code>##

while ( my ( $iter, $elem ) = each @a ){
    say "Iteration $iter contains $elem";
}