>perl -wMstrict -le
"my @text = qw/A B C D E F G H I J/;
 ;;
 I:
 for my $i (0 .. $#text) {
   next I unless $text[$i] eq 'F';
   print qq{$text[$i] is at index $i};
   last I;
   }
"
F is at index 5

##</code><code>##

>perl -wMstrict -le
"my @text = ('A' .. 'J');
 ;;
 I:
 while (my ($i, $element) = each @text) {
   next I unless $element eq 'F';
   print qq{$element is at index $i};
   last I;
   }
"
F is at index 5

##</code><code>##

>perl -wMstrict -le
"my @text = qw/A B C D E F G H F I J/;
 ;;
 my @F_in_it = grep { $text[$_] eq 'F' } 0 .. $#text;
 ;;
 print qq{these indices have an 'F': @F_in_it};
"
these indices have an 'F': 5 8