/ 
perl-5.27.7
⭐ Starred 2013
/ perlcheat
Security Advisories (8)
CVE-2020-12723 (2020-06-05)

regcomp.c in Perl before 5.30.3 allows a buffer overflow via a crafted regular expression because of recursive S_study_chunk calls.

CVE-2020-10878 (2020-06-05)

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.

CVE-2020-10543 (2020-06-05)

Perl before 5.30.3 on 32-bit platforms allows a heap-based buffer overflow because nested regular expression quantifiers have an integer overflow.

CVE-2018-6798 (2018-04-17)

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.

CVE-2023-47100

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.

CVE-2024-56406 (2025-04-13)

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.

CVE-2025-40909 (2025-05-30)

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

CVE-2023-47039 (2023-10-30)

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.

NAME

perlcheat - Perl 5 Cheat Sheet

DESCRIPTION

This 'cheat sheet' is a handy reference, meant for beginning Perl programmers. Not everything is mentioned, but 195 features may already be overwhelming.

The sheet

CONTEXTS  SIGILS  ref        ARRAYS        HASHES
void      $scalar SCALAR     @array        %hash
scalar    @array  ARRAY      @array[0, 2]  @hash{'a', 'b'}
list      %hash   HASH       $array[0]     $hash{'a'}
          &sub    CODE
          *glob   GLOB       SCALAR VALUES
                  FORMAT     number, string, ref, glob, undef
REFERENCES
\      reference       $$foo[1]       aka $foo->[1]
$@%&*  dereference     $$foo{bar}     aka $foo->{bar}
[]     anon. arrayref  ${$$foo[1]}[2] aka $foo->[1]->[2]
{}     anon. hashref   ${$$foo[1]}[2] aka $foo->[1][2]
\()    list of refs
                       SYNTAX
OPERATOR PRECEDENCE    foreach (LIST) { }     for (a;b;c) { }
->                     while   (e) { }        until (e)   { }
++ --                  if      (e) { } elsif (e) { } else { }
**                     unless  (e) { } elsif (e) { } else { }
! ~ \ u+ u-            given   (e) { when (e) {} default {} }
=~ !~
* / % x                 NUMBERS vs STRINGS  FALSE vs TRUE
+ - .                   =          =        undef, "", 0, "0"
<< >>                   +          .        anything else
named uops              == !=      eq ne
< > <= >= lt gt le ge   < > <= >=  lt gt le ge
== != <=> eq ne cmp ~~  <=>        cmp
&
| ^             REGEX MODIFIERS       REGEX METACHARS
&&              /i case insensitive   ^      string begin
|| //           /m line based ^$      $      str end (bfr \n)
.. ...          /s . includes \n      +      one or more
?:              /x /xx ign. wh.space  *      zero or more
= += last goto  /p preserve           ?      zero or one
, =>            /a ASCII    /aa safe  {3,7}  repeat in range
list ops        /l locale   /d  dual  |      alternation
not             /u Unicode            []     character class
and             /e evaluate /ee rpts  \b     boundary
or xor          /g global             \z     string end
                /o compile pat once   ()     capture
DEBUG                                 (?:p)  no capture
-MO=Deparse     REGEX CHARCLASSES     (?#t)  comment
-MO=Terse       .   [^\n]             (?=p)  ZW pos ahead
-D##            \s  whitespace        (?!p)  ZW neg ahead
-d:Trace        \w  word chars        (?<=p) ZW pos behind \K
                \d  digits            (?<!p) ZW neg behind
CONFIGURATION   \pP named property    (?>p)  no backtrack
perl -V:ivsize  \h  horiz.wh.space    (?|p|p)branch reset
                \R  linebreak         (?<n>p)named capture
                \S \W \D \H negate    \g{n}  ref to named cap
                                      \K     keep left part
FUNCTION RETURN LISTS
stat      localtime    caller         SPECIAL VARIABLES
 0 dev    0 second      0 package     $_    default variable
 1 ino    1 minute      1 filename    $0    program name
 2 mode   2 hour        2 line        $/    input separator
 3 nlink  3 day         3 subroutine  $\    output separator
 4 uid    4 month-1     4 hasargs     $|    autoflush
 5 gid    5 year-1900   5 wantarray   $!    sys/libcall error
 6 rdev   6 weekday     6 evaltext    $@    eval error
 7 size   7 yearday     7 is_require  $$    process ID
 8 atime  8 is_dst      8 hints       $.    line number
 9 mtime                9 bitmask     @ARGV command line args
10 ctime               10 hinthash    @INC  include paths
11 blksz               3..10 only     @_    subroutine args
12 blcks               with EXPR      %ENV  environment

ACKNOWLEDGEMENTS

The first version of this document appeared on Perl Monks, where several people had useful suggestions. Thank you, Perl Monks.

A special thanks to Damian Conway, who didn't only suggest important changes, but also took the time to count the number of listed features and make a Perl 6 version to show that Perl will stay Perl.

AUTHOR

Juerd Waalboer <#####@juerd.nl>, with the help of many Perl Monks.

SEE ALSO