perl version cheat sheet

The most significant features introduced for recent versions of the Perl scripting language.

Core security support is provided for 3 years, so typical users should run at least 5.38. Stable distributions such as Debian 11 maintain 5.32+. Enterprise platforms retain versions up to 5.14.

5.42 2025-07-03: latest stable release

use source::encoding 'ascii': disallow non-ASCII in following program code, catching Unicode without appropriate use utf8 (bundled)
:writer: field attribute automatically create writer accessors, analogous to :reader (feature)
any, all: operators to test value existence, basically grep with boolean results; even faster than List::Util synonyms {any {$_ == 3} 1..5} (feature, experimental)
my method: lexical visibility like my sub for private method subroutines; can be called by a new ->& operator
Unicode: v16.0

5.40 2024-06-09: active core support

use v5.40: import builtin functions and enable the try feature
__CLASS__: keyword to reference to the current class name, similar to __PACKAGE__ (feature)
:reader: attribute for field variables to create corresponding accessor methods (feature)
^^: higher precedence logical xor operator, as || is to or (variant ^^= added in v5.42)
builtin::inf, builtin::nan: constants equivalent to special floating point values infinity and Not a Number
use Test2::Suite: comprehensive set of test tools for writing unit tests, providing a drop in replacement to Test::More

5.38 2023-07-02: official security patches

use feature "module_true": packages implicitly return true, enabled along with no feature "bareword_filehandles" (bundled)
sub ($var ||= default): assign values when false (or undefined on //=) instead of omitted
/(*{ … })/: optimistic eval: (?{ … }) with regex optimisations enabled
class: define object classes: packages with field variables and method subroutines (feature, experimental)
${^LAST_SUCCESSFUL_PATTERN}: explicit variable to access the previous match as in s//…/
%{^HOOK}: perform tasks require__before and require__after when calling require
Unicode: v15.0

5.36 2022-05-28

use v5.36: use warnings; use feature qw'signatures isa'; no feature qw'indirect multidimensional switch'
use builtin: namespace for interpreter functions, such as weaken and blessed from Scalar::Util, ceil/floor from POSIX, and trim like String::Util (experimental until 5.40 then bundled)
is_bool(!0): distinguish scalar variable types (by builtin functions) for data interoperability
for my ($k, $v) (%hash): iterate over multiple values at a time (including builtin::indexed for arrays) (feature, experimental until 5.40)
defer {}: queue code to be executed when going out of scope (feature, experimental)
try {} finally {}: run code at the end of a try construct regardless of failure (feature, experimental)
q«…»: unicode delimiters for quoting operators (experimental)
sub ($var) {!pop}: signatured subs are stable, but mixing with the arguments array @_ remains experimental (feature, experimental)
$SIG{FPE}: floating-point exceptions no longer deferred but delivered immediately like other signals
perl -g: disable input record separator (slurp mode), alias for -0777
Unicode: v14.0

5.34 2021-05-20

try {} catch: exception handling similar to eval blocks (feature, experimental until 5.40 then bundled)
/{,n}/: empty lower bound quantifier is accepted as shorthand for 0
\x{ … }: insignificant space within curly braces, also for \b{}, \g{}, \k{}, \N{}, \o{} as well as /{m,n}/ quantifiers
0o0: octal prefix 0o alternative to 0… and oct
re::optimization(qr//): debug regular expression optimization information discovered at compile time
no feature …: disable discouraged practices of multidimensional and bareword_filehandles array emulation (bundled in 5.36 and 5.38)

5.32 2020-06-20: still maintained by common vendors

isa: infix operator to check class instance (feature, experimental until 5.36 then bundled)
$min < $_ <= $max: chained comparison repeats inner part as $min < $_ and $_ <= $max
/\p{Name=$var}/: match Unicode Name property like \N{} but with interpolation and subpatterns
open F, '+>>', undef: respect append mode on temporary files with mixed access
no feature 'indirect': disable indirect object notation such as new Class instead of Class->new (bundled in 5.36)
streamzip: program distributed with core IO::Compress::Base to compress stdin into a zip container
Unicode: v13.0

5.30 2019-05-22

/(?<=var+): variable length lookbehind assertions (experimental until 5.36)
m(\p{nv=/.*/}): match unicode properties by regular expressions (experimental)
my $state if 0: workaround for state (deprecated since v5.10!) is now prohibited
qr'\N': Delimiters must be graphemes; unescaped { illegal; \N in single quotes
Unicode: v12.1

5.28 2018-06-22

delete %hash{…}: hash slices can be deleted with key+value pairs
/(*…)/: alphabetic synonyms for assertions, e.g. (*atomic:…) for (?>…) and (*nlb:…) for (?<!…) (experimental until 5.31.6)
/(*script_run:)/: enforces all characters to be from the same script (experimental until 5.31.6)
state @a: persistent lexical array or hash variables (in addition to scalars)
perl -i -pe die: safe in-place editing: files are replaced only after successful completion
${^SAFE_LOCALES}: locales are thread-safe on supported systems, indicated by this variable
Unicode: v10.0

5.26 2017-05-30

use lib '.': current directory no longer included in default module search path @INC
<<~EOT: indented here-docs, strips same whitespace before delimiter in each line
@{^CAPTURE}: array of last match's captures, so ${^CAPTURE}[0] is $1
//xx: extended modifier to also ignore whitespace in bracketed character classes
use Test2::V0: generic testing framework to replace Test::* and TAP::*
Unicode: v9.0

5.24 2016-05-09

printf '%.*2$x': reordered precision arguments
/\b{lb}/: line break boundary type (position suitable for hyphenation)
/faster/: various significant speedups, notably matching fixed substrings, /i on caseless languages, 64-bit arithmetic, scope overhead
Unicode: v8.0

5.22 2015-06-01

\$alias =: aliasing via reference (scoped as of v5.25.3) (experimental)
<<…>>: safe readline ignoring open flags in arguments
/()/n: flag to disable numbered capturing, turning () into (?:)
/\b{}/: boundary types: gcb (grapheme cluster), sb (sentence), wb (word)
&.: & | ^ ~ consistently numeric, dotted operators for strings (feature, experimental until 5.28 then bundled)
use re 'strict': apply stricter syntax rules to regular expression patterns (experimental)
0x.beep+0: hexadecimal floating point notation with binary power; printf '%a' to display
??: single match shorthand (deprecated since v5.14) requires the operator m?PATTERN?
use CGI: deprecated interface for serving http requests removed from core, see CGI::Alternatives
Unicode: v7.0

5.20 2014-05-27: extended vendor support 202X

sub ($var): subroutine signatures (feature, experimental until 5.36 then bundled)
%hash{…}: hash slices return key+value pairs
[]->@*: postfix dereferencing (also e.g. $scalar->$* for $$scalar) (feature, experimental until 5.24 then bundled)
use warnings 'once'; $a: variables $a and $b are exempt from used once warnings
Unicode: v6.3

5.18 2013-05-18

PERL_PERTURB_KEYS=1: hash overhaul; order is randomised instead of being semi-repeatable {each %{{%hash}} ne each %{{%hash}}}
${^LAST_FH}: last read filehandle (used by $.)
/(?[ a + b ])/: regex set operations (character subtraction -, union +, intersection &, xor ^) (experimental until 5.36)
my sub: lexical subroutines (also state, our); buggy before v5.22 (experimental until 5.26)
next $expression: loop controls allow runtime expressions
no warnings 'experimental::…': mechanism for experimental features, as of now required for smartmatch
Unicode: v6.2

5.16 2012-05-20

__SUB__: current subroutine reference (feature, bundled)
fc, "\F": unicode foldcase to compare case-insensitively (feature, bundled)
"\N{}": automatic use charnames qw( :full :short )
Unicode: v6.1

5.14 2011-05-14

s///r: non-destructive substitution
/(?{ m() })/: regular expressions can be nested in /(?{})/ and /(??{})/ (experimental until 5.20)
/dalu: regexp modifiers to restrict character classes: either default, ascii, locale, or unicode semantics.
use re '/flags': customise default modifiers
/(?^)/: construct to reset to default modifiers
FH->method: filehandle method calls load IO::File on demand (eg. STDOUT->flush)
\o{}: escape sequence for octal values beyond 0777
package {}: package declaration in scope of code block only
multiple: labels:: statement labels allowed in all places, even before other labels
use JSON: interface with data in JavaScript Object Notation {decode_json <>}
Unicode: v6.0+#8

5.12 2010-04-12

package version: package NAME VERSION shorthand for our $VERSION
...: yada-yada operator: code placeholder
use 5.012: implicit strict if use VERSION >= v5.12
… when: when is now allowed to be used as a statement modifier
use overload 'qr': customisable conversion to regular expressions
/\N/: inverse \n to match any character except newline regardless of /s (experimental until 5.18)
Unicode: v5.2

5.10 2007-12-18: supported commercially until 2024

use v5.10: minimal perl version with bundled features (pragma to lexically enable backwards-incompatible syntax)
//: defined-or operator
~~: smart-match operator to compare different data types (updated in v5.10.1) (experimental)
say: print with newline, equivalent to print @_, "\n" (feature, bundled)
given: switch statement to smart-match with when/default (feature, experimental, bundled)
/(?<name>)/: named capture buffers into %+
/(?1)/: recursive regular expression patterns
/(?|)/: resets capture numbering for each contained branch
/.++/: possessive quantifiers ?+, *+, ++ to match greedily
s/keep\K//: floating positive lookbehind, efficient alternative for s/(keep)/$1/
/p: optionally preserve ${^MATCH} variables (avoiding $& penalty until COW in v5.20)
/\v/, /\h/: vertical and horizontal whitespace escapes (\V \H to invert); also /\R/ for newlines
state: persistent my variables (scalars only until 5.28) (feature, bundled)
use autodie: replace builtin functions to throw exceptions instead of returning failure {eval {open ...} or $@->matches("open") || die}
use IO::Compress::Zip: various file compression standards {zip IO::Uncompress::Gunzip->new("test.gz") => "recompressed.zip"}
use Time::Piece: timestamps as objects {localtime->year > 1900}
use File::Fetch: generic data retrieval/download {File::Fetch->new(uri => "http://localhost/")->fetch(to => \$slurp)}
Unicode: v5.0.0

5.8 2002-07-18: stable minimum upto 2021

no utf8: full unicode support, utf8 pragma only for script encoding
use open: file handle behaviour altered by PerlIO layers {binmode $fh, ":bytes"}
open $fh, '-|', @cmd: open list to fork a command without spawning a shell
open $fh, '>', \$var: perl scalars as virtual files
printf '%1$s', @args: syntax to use parameters out of order
1_2_3 == 123: underscores between digits allowed in numeric constants
use bignum: transparent big number support {length 1e100 == 101}
use if: conditional module inclusion {no if $] >= 5.022, "warnings", "redundant"}
use Digest: calculate various message digests (data hashes) {$hash = sha256_hex($data)}
use Encode: character set conversion {encode("utf8", decode("iso-8859-1", $octets))}
use File::Temp: create a temporary file or directory safely {$fh = tempfile();}
use List::Util: general-utility list subroutines {@cards = shuffle 0..51}
use Locale::Maketext: various localization and internationalization in Locale::* and L18N::*
use Memoize: remember function results, trading space for time {memoize "stat"}
use MIME::Base64: base64 encoded strings as in email attachments
use Test::More: modern framework for unit testing {is $got, $expected}
use Time::HiRes: high resolution timers {$μs = [gettimeofday]; sleep .1; $elapsed = tv_interval $μs}
Unicode: v3.2.0

5.6 2000-03-23: start of modern compatibility

use warnings: pragma to enable warnings in lexical scope
use utf8: experimental unicode semantics (completed in v5.8) (experimental until 5.8)
use charnames: string escape \N{} to insert named character
our: declare global variables
v1.2.3: represent strings as vector of ordinals, useful in version numbers (printf '%vd' to display)
0b0: binary numbers in literals, printf '%b', and oct
sub :lvalue: subroutine attribute to return a modifiable value (experimental until 5.20)
open my $fh, $mode, $expr: file handles in scoped scalars, third argument for unambiguous file name
pack 'q': 64-bit integer support (also large files >2GiB) (experimental until 5.8.1)
sort $coderef (): comparison function can be a subroutine reference; prototype ($$) to pass elements as normal @_
CHECK {}: special block called at end of compilation
/[[:…:]]/: POSIX character class syntax such as /[[:alpha:]]/
Unicode: v3.0.1

Perl release summary