Security Advisories (18)
regcomp.c in Perl before 5.30.3 allows a buffer overflow via a crafted regular expression because of recursive S_study_chunk calls.
- https://github.com/Perl/perl5/compare/v5.30.2...v5.30.3
- https://github.com/Perl/perl5/blob/blead/pod/perl5303delta.pod
- https://github.com/Perl/perl5/issues/16947
- https://github.com/perl/perl5/commit/66bbb51b93253a3f87d11c2695cfb7bdb782184a
- https://github.com/Perl/perl5/issues/17743
- https://security.netapp.com/advisory/ntap-20200611-0001/
- https://security.gentoo.org/glsa/202006-03
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/IN3TTBO5KSGWE5IRIKDJ5JSQRH7ANNXE/
- http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00044.html
- https://www.oracle.com/security-alerts/cpuoct2020.html
- https://www.oracle.com/security-alerts/cpujan2021.html
- https://www.oracle.com/security-alerts/cpuApr2021.html
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://perldoc.perl.org/perl5283delta
- https://perldoc.perl.org/perl5303delta
- https://perldoc.perl.org/perl5320delta
Perl before 5.30.3 has an integer overflow related to mishandling of a "PL_regkind[OP(n)] == NOTHING" situation. A crafted regular expression could lead to malformed bytecode with a possibility of instruction injection.
- https://github.com/Perl/perl5/compare/v5.30.2...v5.30.3
- https://github.com/perl/perl5/commit/3295b48defa0f8570114877b063fe546dd348b3c
- https://github.com/perl/perl5/commit/0a320d753fe7fca03df259a4dfd8e641e51edaa8
- https://github.com/Perl/perl5/blob/blead/pod/perl5303delta.pod
- https://security.netapp.com/advisory/ntap-20200611-0001/
- https://security.gentoo.org/glsa/202006-03
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/IN3TTBO5KSGWE5IRIKDJ5JSQRH7ANNXE/
- http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00044.html
- https://www.oracle.com/security-alerts/cpuoct2020.html
- https://www.oracle.com/security-alerts/cpujan2021.html
- https://www.oracle.com/security-alerts/cpuApr2021.html
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://perldoc.perl.org/perl5283delta
- https://perldoc.perl.org/perl5303delta
- https://perldoc.perl.org/perl5320delta
Perl before 5.30.3 on 32-bit platforms allows a heap-based buffer overflow because nested regular expression quantifiers have an integer overflow.
- https://github.com/Perl/perl5/compare/v5.30.2...v5.30.3
- https://github.com/perl/perl5/commit/897d1f7fd515b828e4b198d8b8bef76c6faf03ed
- https://github.com/Perl/perl5/blob/blead/pod/perl5303delta.pod
- https://security.netapp.com/advisory/ntap-20200611-0001/
- https://security.gentoo.org/glsa/202006-03
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/IN3TTBO5KSGWE5IRIKDJ5JSQRH7ANNXE/
- http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00044.html
- https://www.oracle.com/security-alerts/cpuoct2020.html
- https://www.oracle.com/security-alerts/cpujan2021.html
- https://www.oracle.com/security-alerts/cpuApr2021.html
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://perldoc.perl.org/perl5283delta
- https://perldoc.perl.org/perl5303delta
- https://perldoc.perl.org/perl5320delta
An issue was discovered in Perl 5.22 through 5.26. Matching a crafted locale dependent regular expression can cause a heap-based buffer over-read and potentially information disclosure.
- https://www.debian.org/security/2018/dsa-4172
- https://rt.perl.org/Public/Bug/Display.html?id=132063
- http://www.securitytracker.com/id/1040681
- https://access.redhat.com/errata/RHSA-2018:1192
- https://usn.ubuntu.com/3625-1/
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5244delta
- https://perldoc.perl.org/perl5262delta
- https://github.com/Perl/perl5/issues/16143
An issue was discovered in Perl 5.18 through 5.26. A crafted regular expression can cause a heap-based buffer overflow, with control over the bytes written.
- https://www.debian.org/security/2018/dsa-4172
- https://rt.perl.org/Public/Bug/Display.html?id=132227
- http://www.securitytracker.com/id/1040681
- https://access.redhat.com/errata/RHSA-2018:1192
- https://usn.ubuntu.com/3625-1/
- http://www.securitytracker.com/id/1042004
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5244delta
- https://perldoc.perl.org/perl5262delta
Heap-based buffer overflow in the pack function in Perl before 5.26.2 allows context-dependent attackers to execute arbitrary code via a large item count.
- https://www.debian.org/security/2018/dsa-4172
- https://rt.perl.org/Public/Bug/Display.html?id=131844
- https://lists.debian.org/debian-lts-announce/2018/04/msg00009.html
- http://www.securitytracker.com/id/1040681
- https://usn.ubuntu.com/3625-2/
- https://usn.ubuntu.com/3625-1/
- http://www.securityfocus.com/bid/103953
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5244delta
- https://perldoc.perl.org/perl5262delta
- https://github.com/Perl/perl5/issues/16098
Perl before 5.26.3 has a buffer overflow via a crafted regular expression that triggers invalid write operations.
- https://www.debian.org/security/2018/dsa-4347
- https://rt.perl.org/Ticket/Display.html?id=131649
- https://metacpan.org/changes/release/SHAY/perl-5.26.3
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RWQGEB543QN7SSBRKYJM6PSOC3RLYGSM/
- https://github.com/Perl/perl5/commit/19a498a461d7c81ae3507c450953d1148efecf4f
- https://bugzilla.redhat.com/show_bug.cgi?id=1646751
- http://www.securitytracker.com/id/1042181
- https://usn.ubuntu.com/3834-1/
- http://www.securityfocus.com/bid/106145
- https://access.redhat.com/errata/RHSA-2019:0010
- https://access.redhat.com/errata/RHSA-2019:0001
- https://security.netapp.com/advisory/ntap-20190221-0003/
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
Perl before 5.26.3 has a buffer over-read via a crafted regular expression that triggers disclosure of sensitive information from process memory.
- https://www.debian.org/security/2018/dsa-4347
- https://usn.ubuntu.com/3834-2/
- https://rt.perl.org/Ticket/Display.html?id=133192
- https://metacpan.org/changes/release/SHAY/perl-5.26.3
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RWQGEB543QN7SSBRKYJM6PSOC3RLYGSM/
- https://github.com/Perl/perl5/commit/43b2f4ef399e2fd7240b4eeb0658686ad95f8e62
- https://bugzilla.redhat.com/show_bug.cgi?id=1646738
- http://www.securitytracker.com/id/1042181
- https://usn.ubuntu.com/3834-1/
- https://access.redhat.com/errata/RHSA-2019:0010
- https://access.redhat.com/errata/RHSA-2019:0001
- https://security.netapp.com/advisory/ntap-20190221-0003/
- https://support.apple.com/kb/HT209600
- https://seclists.org/bugtraq/2019/Mar/42
- http://seclists.org/fulldisclosure/2019/Mar/49
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
Perl before 5.26.3 and 5.28.0 before 5.28.1 has a buffer overflow via a crafted regular expression that triggers invalid write operations.
- https://www.debian.org/security/2018/dsa-4347
- https://rt.perl.org/Public/Bug/Display.html?id=133423
- https://metacpan.org/changes/release/SHAY/perl-5.28.1
- https://metacpan.org/changes/release/SHAY/perl-5.26.3
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RWQGEB543QN7SSBRKYJM6PSOC3RLYGSM/
- https://bugzilla.redhat.com/show_bug.cgi?id=1646734
- http://www.securitytracker.com/id/1042181
- https://usn.ubuntu.com/3834-1/
- http://www.securityfocus.com/bid/106179
- https://access.redhat.com/errata/RHSA-2019:0010
- https://access.redhat.com/errata/RHSA-2019:0001
- https://security.netapp.com/advisory/ntap-20190221-0003/
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5281delta
- https://perldoc.perl.org/perl5263delta
Perl before 5.26.3 and 5.28.x before 5.28.1 has a buffer overflow via a crafted regular expression that triggers invalid write operations.
- https://www.debian.org/security/2018/dsa-4347
- https://usn.ubuntu.com/3834-2/
- https://rt.perl.org/Ticket/Display.html?id=133204
- https://metacpan.org/changes/release/SHAY/perl-5.28.1
- https://metacpan.org/changes/release/SHAY/perl-5.26.3
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RWQGEB543QN7SSBRKYJM6PSOC3RLYGSM/
- https://lists.debian.org/debian-lts-announce/2018/11/msg00039.html
- https://github.com/Perl/perl5/commit/34716e2a6ee2af96078d62b065b7785c001194be
- https://bugzilla.redhat.com/show_bug.cgi?id=1646730
- http://www.securitytracker.com/id/1042181
- https://usn.ubuntu.com/3834-1/
- http://www.securityfocus.com/bid/106145
- https://access.redhat.com/errata/RHSA-2019:0010
- https://access.redhat.com/errata/RHSA-2019:0001
- https://access.redhat.com/errata/RHSA-2019:0109
- https://security.netapp.com/advisory/ntap-20190221-0003/
- https://support.apple.com/kb/HT209600
- https://seclists.org/bugtraq/2019/Mar/42
- http://seclists.org/fulldisclosure/2019/Mar/49
- https://kc.mcafee.com/corporate/index?page=content&id=SB10278
- https://access.redhat.com/errata/RHBA-2019:0327
- https://access.redhat.com/errata/RHSA-2019:1790
- https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
- https://access.redhat.com/errata/RHSA-2019:1942
- https://access.redhat.com/errata/RHSA-2019:2400
- https://security.gentoo.org/glsa/201909-01
- https://www.oracle.com/security-alerts/cpuapr2020.html
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5281delta
- https://perldoc.perl.org/perl5263delta
Buffer overflow in the S_grok_bslash_N function in regcomp.c in Perl 5 before 5.24.3-RC1 and 5.26.x before 5.26.1-RC1 allows remote attackers to disclose sensitive information or cause a denial of service (application crash) via a crafted regular expression with an invalid '\\N{U+...}' escape.
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.26.1-RC1
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.24.3-RC1
- https://perl5.git.perl.org/perl.git/commitdiff/2be4edede4ae226e2eebd4eff28cedd2041f300f#patch1
- https://bugzilla.redhat.com/show_bug.cgi?id=1492093
- http://www.securityfocus.com/bid/100852
- http://mirror.cucumberlinux.com/cucumber/cucumber-1.0/source/lang-base/perl/patches/CVE-2017-12883.patch
- https://rt.perl.org/Public/Bug/Display.html?id=131598
- http://www.debian.org/security/2017/dsa-3982
- https://security.netapp.com/advisory/ntap-20180426-0001/
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://github.com/Perl/perl5/issues/16025
- https://perldoc.perl.org/perl5243delta
- https://perldoc.perl.org/perl5280delta
- https://perldoc.perl.org/perl5261delta
Heap-based buffer overflow in the S_regatom function in regcomp.c in Perl 5 before 5.24.3-RC1 and 5.26.x before 5.26.1-RC1 allows remote attackers to cause a denial of service (out-of-bounds write) via a regular expression with a '\\N{}' escape and the case-insensitive modifier.
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.26.1-RC1
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.24.3-RC1
- https://perl5.git.perl.org/perl.git/commitdiff/96c83ed78aeea1a0496dd2b2d935869a822dc8a5
- https://bugzilla.redhat.com/show_bug.cgi?id=1492091
- http://www.securityfocus.com/bid/100860
- https://rt.perl.org/Public/Bug/Display.html?id=131582
- http://www.debian.org/security/2017/dsa-3982
- https://security.netapp.com/advisory/ntap-20180426-0001/
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://github.com/Perl/perl5/issues/16021
- https://perldoc.perl.org/perl5243delta
- https://perldoc.perl.org/perl5261delta
- https://perldoc.perl.org/perl5280delta
Stack-based buffer overflow in the CPerlHost::Add method in win32/perlhost.h in Perl before 5.24.3-RC1 and 5.26.x before 5.26.1-RC1 on Windows allows attackers to execute arbitrary code via a long environment variable.
- https://rt.perl.org/Public/Bug/Display.html?id=131665
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.26.1-RC1
- https://perl5.git.perl.org/perl.git/log/refs/tags/v5.24.3-RC1
- http://www.securityfocus.com/bid/101051
- https://security.netapp.com/advisory/ntap-20180426-0001/
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://perldoc.perl.org/perl5243delta
- https://github.com/Perl/perl5/issues/16051
- https://perldoc.perl.org/perl5261delta
- https://perldoc.perl.org/perl5280delta
In Perl before 5.38.2, S_parse_uniprop_string in regcomp.c can write to unallocated space because a property name associated with a \p{...} regular expression construct is mishandled. The earliest affected version is 5.30.0.
A heap buffer overflow vulnerability was discovered in Perl. When there are non-ASCII bytes in the left-hand-side of the `tr` operator, `S_do_trans_invmap` can overflow the destination pointer `d`. $ perl -e '$_ = "\x{FF}" x 1000000; tr/\xFF/\x{100}/;' Segmentation fault (core dumped) It is believed that this vulnerability can enable Denial of Service and possibly Code Execution attacks on platforms that lack sufficient defenses.
- https://github.com/Perl/perl5/commit/87f42aa0e0096e9a346c9672aa3a0bd3bef8c1dd.patch
- https://metacpan.org/release/SHAY/perl-5.38.4/changes
- https://metacpan.org/release/SHAY/perl-5.40.2/changes
- http://www.openwall.com/lists/oss-security/2025/04/13/3
- http://www.openwall.com/lists/oss-security/2025/04/13/4
Perl threads have a working directory race condition where file operations may target unintended paths. If a directory handle is open at thread creation, the process-wide current working directory is temporarily changed in order to clone that handle for the new thread, which is visible from any third (or more) thread already running. This may lead to unintended operations such as loading code or accessing files from unexpected locations, which a local attacker may be able to exploit. The bug was introduced in commit 11a11ecf4bea72b17d250cfb43c897be1341861e and released in Perl version 5.13.6
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1098226
- https://github.com/Perl/perl5/commit/11a11ecf4bea72b17d250cfb43c897be1341861e
- https://github.com/Perl/perl5/commit/918bfff86ca8d6d4e4ec5b30994451e0bd74aba9.patch
- https://github.com/Perl/perl5/issues/10387
- https://github.com/Perl/perl5/issues/23010
- https://perldoc.perl.org/5.14.0/perl5136delta#Directory-handles-not-copied-to-threads
- https://www.openwall.com/lists/oss-security/2025/05/22/2
- http://www.openwall.com/lists/oss-security/2025/05/23/1
- http://www.openwall.com/lists/oss-security/2025/05/30/4
Perl for Windows relies on the system path environment variable to find the shell (cmd.exe). When running an executable which uses Windows Perl interpreter, Perl attempts to find and execute cmd.exe within the operating system. However, due to path search order issues, Perl initially looks for cmd.exe in the current working directory. An attacker with limited privileges can exploit this behavior by placing cmd.exe in locations with weak permissions, such as C:\ProgramData. By doing so, when an administrator attempts to use this executable from these compromised locations, arbitrary code can be executed.
(1) cpan/Archive-Tar/bin/ptar, (2) cpan/Archive-Tar/bin/ptardiff, (3) cpan/Archive-Tar/bin/ptargrep, (4) cpan/CPAN/scripts/cpan, (5) cpan/Digest-SHA/shasum, (6) cpan/Encode/bin/enc2xs, (7) cpan/Encode/bin/encguess, (8) cpan/Encode/bin/piconv, (9) cpan/Encode/bin/ucmlint, (10) cpan/Encode/bin/unidump, (11) cpan/ExtUtils-MakeMaker/bin/instmodsh, (12) cpan/IO-Compress/bin/zipdetails, (13) cpan/JSON-PP/bin/json_pp, (14) cpan/Test-Harness/bin/prove, (15) dist/ExtUtils-ParseXS/lib/ExtUtils/xsubpp, (16) dist/Module-CoreList/corelist, (17) ext/Pod-Html/bin/pod2html, (18) utils/c2ph.PL, (19) utils/h2ph.PL, (20) utils/h2xs.PL, (21) utils/libnetcfg.PL, (22) utils/perlbug.PL, (23) utils/perldoc.PL, (24) utils/perlivp.PL, and (25) utils/splain.PL in Perl 5.x before 5.22.3-RC2 and 5.24 before 5.24.1-RC2 do not properly remove . (period) characters from the end of the includes directory array, which might allow local users to gain privileges via a Trojan horse module under the current working directory.
- https://perldoc.perl.org/5.24.1/perldelta
- http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00002.html
- http://perl5.git.perl.org/perl.git/commit/cee96d52c39b1e7b36e1c62d38bcd8d86e9a41ab
- http://www.debian.org/security/2016/dsa-3628
- http://www.nntp.perl.org/group/perl.perl5.porters/2016/07/msg238271.html
- http://www.securityfocus.com/bid/92136
- http://www.securitytracker.com/id/1036440
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05240731
- https://lists.apache.org/thread.html/7f6a16bc0fd0fd5e67c7fd95bd655069a2ac7d1f88e42d3c853e601c%40%3Cannounce.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2018/11/msg00016.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2FBQOCV3GBAN2EYZUM3CFDJ4ECA3GZOK/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DOFRQWJRP2NQJEYEWOMECVW3HAMD5SYN/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TZBNQH3DMI7HDELJAZ4TFJJANHXOEDWH/
- https://rt.perl.org/Public/Bug/Display.html?id=127834
- https://security.gentoo.org/glsa/201701-75
- https://security.gentoo.org/glsa/201812-07
- http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00002.html
- http://perl5.git.perl.org/perl.git/commit/cee96d52c39b1e7b36e1c62d38bcd8d86e9a41ab
- http://www.debian.org/security/2016/dsa-3628
- http://www.nntp.perl.org/group/perl.perl5.porters/2016/07/msg238271.html
- http://www.securityfocus.com/bid/92136
- http://www.securitytracker.com/id/1036440
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05240731
- https://lists.apache.org/thread.html/7f6a16bc0fd0fd5e67c7fd95bd655069a2ac7d1f88e42d3c853e601c%40%3Cannounce.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2018/11/msg00016.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2FBQOCV3GBAN2EYZUM3CFDJ4ECA3GZOK/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DOFRQWJRP2NQJEYEWOMECVW3HAMD5SYN/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TZBNQH3DMI7HDELJAZ4TFJJANHXOEDWH/
- https://rt.perl.org/Public/Bug/Display.html?id=127834
- https://security.gentoo.org/glsa/201701-75
- https://security.gentoo.org/glsa/201812-07
NAME
getopt, getopts - Process single-character switches with switch clustering
SYNOPSIS
use Getopt::Std;
getopts('oif:'); # -o & -i are boolean flags, -f takes an argument
# Sets $opt_* as a side effect.
getopts('oif:', \%opts); # options as above. Values in %opts
getopt('oDI'); # -o, -D & -I take arg.
# Sets $opt_* as a side effect.
getopt('oDI', \%opts); # -o, -D & -I take arg. Values in %opts
DESCRIPTION
The getopts() function processes single-character switches with switch clustering. Pass one argument which is a string containing all switches to be recognized. For each switch found, if an argument is expected and provided, getopts() sets $opt_x (where x is the switch name) to the value of the argument. If an argument is expected but none is provided, $opt_x is set to an undefined value. If a switch does not take an argument, $opt_x is set to 1.
Switches which take an argument don't care whether there is a space between the switch and the argument. If unspecified switches are found on the command-line, the user will be warned that an unknown option was given.
The getopts() function returns true unless an invalid option was found.
The getopt() function is similar, but its argument is a string containing all switches that take an argument. If no argument is provided for a switch, say, y, the corresponding $opt_y will be set to an undefined value. Unspecified switches are silently accepted. Use of getopt() is not recommended.
Note that, if your code is running under the recommended use strict vars pragma, you will need to declare these package variables with our:
our($opt_x, $opt_y);
For those of you who don't like additional global variables being created, getopt() and getopts() will also accept a hash reference as an optional second argument. Hash keys will be x (where x is the switch name) with key values the value of the argument or 1 if no argument is specified.
To allow programs to process arguments that look like switches, but aren't, both functions will stop processing switches when they see the argument --. The -- will be removed from @ARGV.
--help and --version
If - is not a recognized switch letter, getopts() supports arguments --help and --version. If main::HELP_MESSAGE() and/or main::VERSION_MESSAGE() are defined, they are called; the arguments are the output file handle, the name of option-processing package, its version, and the switches string. If the subroutines are not defined, an attempt is made to generate intelligent messages; for best results, define $main::VERSION.
If embedded documentation (in pod format, see perlpod) is detected in the script, --help will also show how to access the documentation.
Note that due to excessive paranoia, if $Getopt::Std::STANDARD_HELP_VERSION isn't true (the default is false), then the messages are printed on STDERR, and the processing continues after the messages are printed. This being the opposite of the standard-conforming behaviour, it is strongly recommended to set $Getopt::Std::STANDARD_HELP_VERSION to true.
One can change the output file handle of the messages by setting $Getopt::Std::OUTPUT_HELP_VERSION. One can print the messages of --help (without the Usage: line) and --version by calling functions help_mess() and version_mess() with the switches string as an argument.
Module Install Instructions
To install vars, copy and paste the appropriate command in to your terminal.
cpanm vars
perl -MCPAN -e shell
install vars
For more information on module installation, please visit the detailed CPAN module installation guide.