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Author image Brian Szymanski


Number::Range::Regex - create regular expressions that check for integers in a given range


  use Number::Range::Regex;
  my $lt_20 = range( 0, 19 );

  print "foo($foo) contains an integer < 20" if $foo =~ /$lt_20/;
  print "foo($foo) is an integer < 20" if $foo =~ /^$lt_20$/;
  if( $line =~ /^\S+\s+($lt_20)\s/ ) {
    print "the second field ($1) is an integer < 20";
  my $nice_numbers = rangespec( "42,175..192" );
  my $my_values = $lt_20->union( $nice_numbers );
  if( $line =~ /^\S+\s+($my_values)\s/ ) {
    print "the second field has one of my values ($1)";

  my $lt_10        = rangespec( "0..9" );
  my $primes_lt_30 = rangespec( "2,3,5,7,11,13,17,19,23,29" );
  my $primes_lt_10 = $lt_10->intersection( $primes_lt_30 );
  my $nonprimes_lt_10 = $lt_10->minus( $primes_lt_30 );
  print "nonprimes under 10 contains: ".join",", $nonprimes_lt_10->to_string;
  if( $something =~ /^$nonprimes_lt_10$/ ) {
    print "something($something) is a nonprime less than 10";
  if( $nonprimes_lt_10->contains( $something ) ) {
    print "something($something) is a nonprime less than 10";

  my $octet = range(0, 255);
  my $ip4_match = qr/^$octet\.$octet\.$octet\.$octet$/;
  my $range_96_to_127 = range(96, 127);
  my $my_slash26_match = qr/^192\.168\.42\.$range_96_to_127$/;
  my $my_slash19_match = qr/^192\.168\.$range_96_to_127\.$octet$/;

  my $in_a_or_in_b_but_not_both = $a->xor($b);

  my $it = rangespec("-20..42,47..52")->iterator();
  do { print $it->fetch } while ($it->next);
  do { print $it->fetch } while ($it->prev);


Number::Range::Regex lets you manage sets of integers and generate regular expressions matching them. For example, here is one way to match number ranges in a regular expression:

  $date =~ m/^0*(?:[1-9]|[12][0-9]|3[01])\/0*(?:[0-9]|1[012])$/;

here is another:

  my $day_range = range(1, 31);
  my $month_range = range(1, 12);
  $date =~ m/^$day_range\/$month_range$/;

which is more legible? (bonus points if you spotted the bug)



  $range = range( $min, $max );

Create a range between the first argument and the last. For example, $min==8 and $max==12, corresponds to the list containing 8, 9, 10, 11, and 12. This method is exported by default.

  $range = rangespec( '8..12,14,19..22' );

Create a "compound" range given the range specification passed. For example, the range above would consist of 8, 9, 10, 11, 12, 14, 19, 20, 21, and 22. This method is exported by default.


  $range->contains( $number );

Returns a true value if $range contains $number - otherwise, it returns a false value.

  $range->overlaps( $another_range );

Returns a true value if $range overlaps with $another_range - otherwise, it returns a false value. e.g.

  rangespec('7..9')->overlaps( rangespec('4..6') )   => false
  rangespec('7..9')->overlaps( rangespec('10..12') ) => false
  rangespec('7..9')->overlaps( rangespec('6..10') )  => true
  rangespec('7..9')->overlaps( rangespec('6..7') )   => true



Return a compact representation of the range suitable for consumption by a human, perl(1), or rangespec(). For example:

  $range = range( 6, 22 );
  print $range->to_string;

will output: "6..22", which can be parsed by perl(1) or rangespec().


Return a regular expression matching members of this range. For example:

  $range = range( 6, 22 );
  print $range->regex;

will output something equivalent to:


which, on my machine with perl v5.14.2 and a development version of Number::Range::Regex between v0.12 and v0.13, is:

  (?^:(?# begin Number::Range::Regex::SimpleRange[6..22] )[+]?0*(?:(?^:[6-9])|(?^:1\d)|(?^:2[0-2]))(?# end Number::Range::Regex::SimpleRange[6..22] ))


Please note that range objects are overloaded so that in regex context, $range will be equivalent to $range->regex(). This works in all versions of perl >= v5.6.0. When it is further possible to distinguish regex context from string context (as in overload v1.10 or higher, available in perl >= v5.12.0), range objects will display in string but not regex context as the terser, more legible $range->to_string() instead.

If you find any cryptic errors about overloading, please use an explicit ->to_string or ->regex() and file a bug.

UNBOUNDED (aka "infinite") RANGES

It is also possible to specify unbounded ranges, ie the set of all integers less than 17. This may be specified in any of the following ways:

  range( undef, 17 );
  range( '-inf', 17);

Similarly the set of all integers greater than 17:

  range( 17, undef );
  range( 17, '+inf' );

Note carefully that, in order to prevent errors, it is not possible to specify the set of all integers via range(undef, undef). If you try to do so, Number::Range::Regex will complain that you "must specify either a min or a max or use the allow_wildcard argument":

  range( undef, undef );   #boom

If you really want range() with no defined arguments to mean the set of all possible integers, you can use one of the below:

  range( undef, undef, {allow_wildcard => 1} ) ;
  range( '-inf', '+inf' );

To test if a range is infinite, you can call is_infinite():

  1 == ! rangespec('3..7')->is_infinite();
  1 == rangespec('16..+inf')->is_infinite();
  1 == rangespec('')->not->is_infinite();


given $range2 = rangespec( '0,2,4,6,8' ) and $range3 = rangespec( '0,3,6,9' )

  $range = $range2->union( $range3 );

Return the union of one range with another. In the example above, $range would consist of: 0, 2, 3, 4, 6, 8, and 9. Note that union() can take more than one argument, e.g. $range2->union( $range3, $range5, $range7, $range11, ... );

  $range = $range2->intersect( $range3 );

Return the intersection of one range with another. In the example above, $range would consist of: 0 and 6. This method is also available via the alias intersection.

  $range = $range->xor( $another_range );

Return the symmetric difference of $range2 and $range3 (elements in one or the other range, but not in both). In the example above, $range would consist of 2, 3, 4, 8, and 9.

  $range = $range2->subtract( $range3 );

Return the relative complement of $range2 in $range3. In the example above, $range would consist of: 2, 4, and 8. Note carefully that this method is not symmetric - $range3->subtract( $range2 ) would be a different range consisting of 3 and 9. This method is also available via the aliases subtraction and minus.

  $range = $range2->invert();

Return the absolute complement of $range2. In the example above, $range would include:

      any integer less than or equal to -1
      1, 3, 5, and 7,  and
      any integer greater than or equal to 9.

that is, $range->to_string would be '-inf..-1,1,3,5,7,9..+inf'. This method is also available via the alias not.


iterators let you examine large or infinite sets with minimal memory:

  $it = $range->iterator();
  do {
    do_something_with_value( $it->fetch );
  } while ($it->next);

for more information, see Number::Range::Regex::Iterator


  $regex = regex_range( $min, $max );

This is a shortcut for range( $min, $max )->regex(). Useful for one-off use when overload.pm does not support regex context. It should only be used with perl 5.10.X or lower where regex context overloading is not possible. This method may be deprecated in a future release of Number::Range::Regex. This method is not exported by default.


It's usually better to check for number-ness only in the regular expression and verify the range of the number separately, eg: $line =~ /^\S+\s+(\d+)/ && $1 > 15 && $1 < 32; but it's not always practical to refactor in that way.

If you like one-liners, something like the following may suit you... m{^${\( range(1, 31) )}\/${\( range(1, 12) )}$} but, for readability's sake, please don't do that!


Please report any bugs or feature requests through the web interface at http://rt.cpan.org.


Brian Szymanski <ski-cpan@allafrica.com> -- be sure to put Number::Range::Regex in the subject line if you want me to read your message.


Copyright 2012 Brian Szymanski. All rights reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


perl(1), Number::Range, etc.