I like this sort of pattern (update: maybe "style" would be a better word to use here than "pattern"):

c:\@Work\Perl\monks>perl -wMstrict -le
"my @SlectedColumns = (9, 7, 6, 0, 5, 0, 4, 3, 2, 0, 1, 9, 9);
 my $end_index = 10;
 ;;
 COLUMN:
 for my $col (@SlectedColumns[1 .. $end_index]) {
   next COLUMN unless $col != 0;
   print qq{do something with col $col};
   }
"
do something with col 7
do something with col 6
do something with col 5
do something with col 4
do something with col 3
do something with col 2
do something with col 1
[download]

An  if (COND) { ... } structure with its messy indentation and visual presentation is avoided, and cyclomatic complexity is reduced.

Update 1: In my experience, this pattern turns up quite often in a context like:

use constant RX_COMMENT => qr{ ... }xms;
...
...
sub is_valid {
  
    my ($string,
        ) = @_;
        
    return
        $string =~ RX_COMMENT      ? 0 :
        $string =~ RX_BLANK_STRING ? 0 :
        $string =~ RX_VALID_LINE   ? 1 :
        die "invalid: '$string'"   # default
        ;
  
    }
...
...
LINE:
while (my $line = <$fh>) {

    next LINE unless is_valid($line);

    do_something_with_known_valid($line);
    do_something_else_with($line);
    ...

    }  # end while LINE
[download]

Update 2: This is my 4000th writeup!

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