my @strings = (
  join ('', 'a' .. 'z' ),
  join ('', 'a' .. 'z', 0 .. 3 ),
  join ('', 'a' .. 'z', 0 .. 9 ),
);
foreach my $string (@strings) {
  print "\nstring : $string\n";
  print 'length : ', length($string), "\n";
  print 'substr : ', substr( $string, 0, 30 ), "\n";
  print 'regex  : ', ( $string =~ m/.{30}/ ), "\n";
  print 'regex  : ', ( $string =~ m/(.{30})/ ), "\n";
}