SemVer - Use semantic version numbers


  use SemVer; our $VERSION = SemVer->new('1.2.0-b1');


This module subclasses version to create semantic versions, as defined by the Semantic Versioning 2.0.0 Specification. The three salient points of the specification, for the purposes of version formatting, are:

  1. A normal version number MUST take the form X.Y.Z where X, Y, and Z are non-negative integers, and MUST NOT contain leading zeroes. X is the major version, Y is the minor version, and Z is the patch version. Each element MUST increase numerically. For instance: 1.9.0 -> 1.10.0 -> 1.11.0.

  2. A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers immediately following the patch version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Numeric identifiers MUST NOT include leading zeroes. Pre-release versions have a lower precedence than the associated normal version. A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version: 1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-0.3.7, 1.0.0-x.7.z.92

  3. Build metadata MAY be denoted by appending a plus sign and a series of dot separated identifiers immediately following the patch or pre-release version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Build metadata SHOULD be ignored when determining version precedence. Thus two versions that differ only in the build metadata, have the same precedence. Examples: 1.0.0-alpha+001, 1.0.0+20130313144700, 1.0.0-beta+exp.sha.5114f85.


For strict parsing of semantic version numbers, use the new() constructor. If you need something more flexible, use declare(). And if you need something more comparable with what version expects, try parse(). Compare how these constructors deal with various version strings (with values shown as returned by normal():

    Argument  | new      | declare     | parse
  '1.0.0'     | 1.0.0    | 1.0.0       | 1.0.0
  '5.5.2-b1'  | 5.5.2-b1 | 5.5.2-b1    | 5.5.2-b1
  '1.05.0'    | <error>  | 1.5.0       | 1.5.0
  '1.0'       | <error>  | 1.0.0       | 1.0.0
  '  012.2.2' | <error>  | 12.2.2      | 12.2.2
  '1.1'       | <error>  | 1.1.0       | 1.100.0
   1.1        | <error>  | 1.1.0       | 1.100.0
  '1.1.0+b1'  | 1.1.0+b1 | 1.1.0+b1    | 1.1.0+b1
  '1.1-b1'    | <error>  | 1.1.0-b1    | 1.100.0-b1
  '1.2.b1'    | <error>  | 1.2.0-b1    | 1.2.0-b1
  '9.0-beta4' | <error>  | 9.0.0-beta4 | 9.0.0-beta4
  '9'         | <error>  | 9.0.0       | 9.0.0
  '1-b'       | <error>  | 1.0.0-b     | 1.0.0-b
   0          | <error>  | 0.0.0       | 0.0.0
  '0-rc1'     | <error>  | 0.0.0-rc1   | 0.0.0-rc1
  '1.02_30'   | <error>  | 1.23.0      | 1.23.0
   1.02_30    | <error>  | 1.23.0      | 1.23.0

Note that, unlike in version, the declare and parse methods ignore underscores. That is, version strings with underscores are treated as decimal numbers. Hence, the last two examples yield exactly the same semantic versions.

As with version objects, the comparison and stringification operators are all overloaded, so that you can compare semantic versions. You can also compare semantic versions with version objects (but not the other way around, alas). Boolean operators are also overloaded, such that all semantic version objects except for those consisting only of zeros (ignoring prerelease and metadata) are considered true.




  my $semver = SemVer->new('1.2.2');

Performs a validating parse of the version string and returns a new semantic version object. If the version string does not adhere to the semantic version specification an exception will be thrown. See declare and parse for more forgiving constructors.


  my $semver = SemVer->declare('1.2'); # 1.2.0

This parser strips out any underscores from the version string and passes it to to version's declare constructor, which always creates dotted-integer version objects. This is the most flexible way to declare versions. Consider using it to normalize version strings.


  my $semver = SemVer->parse('1.2'); # 1.200.0

This parser dispatches to version's parse constructor, which tries to be more flexible in how it converts simple decimal strings and numbers. Not really recommended, since it's treatment of decimals is quite different from the dotted-integer format of semantic version strings, and thus can lead to inconsistencies. Included only for proper compatibility with version.

Instance Methods


  SemVer->declare('v1.2')->normal;       # 1.2.0
  SemVer->parse('1.2')->normal;          # 1.200.0
  SemVer->declare('1.02.0-b1')->normal;  # 1.2.0-b1
  SemVer->parse('1.02_30')->normal       # 1.230.0
  SemVer->parse(1.02_30)->normal         # 1.23.0

Returns a normalized representation of the version string. This string will always be a strictly-valid dotted-integer semantic version string suitable for passing to new(). Unlike version's normal method, there will be no leading "v".


  SemVer->declare('v1.2')->stringify;    # v1.2
  SemVer->parse('1.200')->stringify;     # v1.200
  SemVer->declare('1.2-r1')->stringify;  # v1.2-r1
  SemVer->parse(1.02_30)->stringify;     # v1.0230
  SemVer->parse(1.02_30)->stringify;     # v1.023

Returns a string that is as close to the original representation as possible. If the original representation was a numeric literal, it will be returned the way perl would normally represent it in a string. This method is used whenever a version object is interpolated into a string.


Throws an exception. Semantic versions cannot be numified. Just don't go there.


  my $is_alpha = $semver->is_alpha;

Returns true if a prerelease and/or metadata string is appended to the end of the version string. This also means that the version number is a "special version", in the semantic versioning specification meaning of the phrase.


  say "Version $semver" if $semver;
  say "Not a $semver" if !$semver;

Returns true for a non-zero semantic semantic version object, without regard to the prerelease or build metadata parts. Overloads boolean operations.


Compares the semantic version object to another version object or string and returns 0 if they're the same, -1 if the invocant is smaller than the argument, and 1 if the invocant is greater than the argument.

Mostly you don't need to worry about this: Just use the comparison operators instead:

  if ($semver < $another_semver) {
      die "Need $another_semver or higher";

Note that in addition to comparing other semantic version objects, you can also compare regular version objects:

  if ($semver < $version) {
      die "Need $version or higher";

You can also pass in a version string. It will be turned into a semantic version object using declare. So if you're using numeric versions, you may or may not get what you want:

  my $semver  = version::Semver->new('1.2.0');
  my $version = '1.2';
  my $bool    = $semver == $version; # true

If that's not what you want, pass the string to parse first:

  my $semver  = Semver->new('1.2.0');
  my $version = Semver->parse('1.2'); # 1.200.0
  my $bool    = $semver == $version; # false

See Also


This module is managed in an open GitHub repository. Feel free to fork and contribute, or to clone and send patches!

Found a bug? Please post a report!


Many thanks to version author John Peacock for his suggestions and debugging help.


  • David E. Wheeler <>

  • Johannes Kilian <>

Copyright and License

Copyright (c) 2010-2020 David E. Wheeler. Some Rights Reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.