Just a cautionary example of greedy  .* versus lazy  .*? regex matching:

>perl -wMstrict -le
"my $s = 'xx FOR foo IN bar baz and FOR fee fie foe IN fum yy';
 ;;
 my @for_in = $s =~ m{ FOR .* IN }xmsg;
 printf 'greedy:  ';
 printf qq{'$_'  } for @for_in;
 print '';
 ;;
 printf 'lazy:  ';
 @for_in = $s =~ m{ FOR .*? IN }xmsg;
 printf qq{'$_'  } for @for_in;
"
greedy:  'FOR foo IN bar baz and FOR fee fie foe IN'
lazy:  'FOR foo IN'  'FOR fee fie foe IN'
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Also note that in the conditional statement
    if (my @captures = $string =~ m{ pattern }xmsg) {
        do_something_with(@captures);
        }
if nothing matches (no captures, array empty), the conditional evaluates false and the statement body is not executed.