LINE: {
    # ...
    redo LINE   if # ...
    # ...
}

##</code><code>##

  my $done = 0;
# ...
  sub {
      my( @data, $row, $key );
      my $found= 0;
      while(  ! $found  &&  ! $done  &&  defined( $row= <$fh> )  ) {
          chomp($row);
          ( $found, $done )= predicate( $row, \$key, \@data );
      }
      return( $key, \@data )   if  $allow;
      return;

##</code><code>##

while(
    conditional
) {
    code
}

##</code><code>##

for(
    init;
    condition;
    cont;
) {
    code;
}

##</code><code>##

init;
while(
    contition
) {
    code;
} continue {
    cont;
}

##</code><code>##

  my $done= 0;
  # ...
      my( @data, $row, $key );
      return   if   $done  ||  ! defined( $row= <$fh> );
      do {
          chomp( $row );
          # [SNIPPED] munge $row, set $key and @data
      } while(  $key < $min  &&  defined( $row= <$fh> )  );
      if(  $max < $key  ) {
          $done = 1;
          return;
      }
      return( $key, \@data );
  }