X<$^V> X<$PERL_VERSION>
The revision, version, and subversion of the Perl interpreter,
-represented as a C<version> object.
+represented as a L<version> object.
This variable first appeared in perl v5.6.0; earlier versions of perl
will see an undefined value. Before perl v5.10.0 C<$^V> was represented
-as a v-string.
+as a v-string rather than a L<version> object.
C<$^V> can be used to determine whether the Perl interpreter executing
a script is in the right range of versions. For example:
warn "Hashes not randomized!\n" if !$^V or $^V lt v5.8.1
-To convert C<$^V> into its string representation use C<sprintf()>'s
-C<"%vd"> conversion:
+While version objects overload stringification, to portably convert
+C<$^V> into its string representation, use C<sprintf()>'s C<"%vd">
+conversion, which works for both v-strings or version objects:
printf "version is v%vd\n", $^V; # Perl's version
See the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
-See also C<$]> for an older representation of the Perl version.
+See also C<$]> for a decimal representation of the Perl version.
-This variable was added in Perl v5.6.0.
+The main advantage of C<$^V> over C<$]> is that, for Perl v5.10.0 or
+later, it overloads operators, allowing easy comparison against other
+version representations (e.g. decimal, literal v-string, "v1.2.3", or
+objects). The disadvantage is that prior to v5.10.0, it was only a
+literal v-string, which can't be easily printed or compared.
-Mnemonic: use ^V for Version Control.
+Mnemonic: use ^V for a version object.
=item ${^WIN32_SLOPPY_STAT}
X<${^WIN32_SLOPPY_STAT}> X<sitecustomize> X<sitecustomize.pl>
=item ${^ENCODING}
X<${^ENCODING}>
+DEPRECATED!!!
+
The I<object reference> to the C<Encode> object that is used to convert
the source code to Unicode. Thanks to this variable your Perl script
-does not have to be written in UTF-8. Default is I<undef>. Setting
-this variable to any other value is deprecated.
+does not have to be written in UTF-8. Default is C<undef>.
+
+Setting this variable to any other value than C<undef> is deprecated due
+to fundamental defects in its design and implementation. It is planned
+to remove it from a future Perl version. Its purpose was to allow your
+non-ASCII Perl scripts to not have to be written in UTF-8; this was
+useful before editors that worked on UTF-8 encoded text were common, but
+that was long ago. It causes problems, such as affecting the operation
+of other modules that aren't expecting it, causing general mayhem. Its
+use can lead to segfaults.
+
+If you need something like this functionality, you should use the
+L<encoding> pragma, which is also deprecated, but has fewer nasty side
+effects.
+
+If you are coming here because code of yours is being adversely affected
+by someone's use of this variable, you can usually work around it by
+doing this:
+
+ local ${^ENCODING};
+
+near the beginning of the functions that are getting broken. This
+undefines the variable during the scope of execution of the including
+function.
This variable was added in Perl 5.8.2.
The C<%^H> hash provides the same scoping semantic as C<$^H>. This makes
it useful for implementation of lexically scoped pragmas. See
-L<perlpragma>.
+L<perlpragma>. All the entries are stringified when accessed at
+runtime, so only simple values can be accommodated. This means no
+pointers to objects, for example.
When putting items into C<%^H>, in order to avoid conflicting with other
users of the hash there is a convention regarding which keys to use.
=item $]
X<$]>
-See L</$^V> for a more modern representation of the Perl version that allows
-accurate string comparisons.
+The revision, version, and subversion of the Perl interpreter, represented
+as a decimal of the form 5.XXXYYY, where XXX is the version / 1e3 and YYY
+is the subversion / 1e6. For example, Perl v5.10.1 would be "5.010001".
-The version + patchlevel / 1000 of the Perl interpreter. This variable
-can be used to determine whether the Perl interpreter executing a
-script is in the right range of versions:
+This variable can be used to determine whether the Perl interpreter
+executing a script is in the right range of versions:
warn "No PerlIO!\n" if $] lt '5.008';
-The floating point representation can sometimes lead to inaccurate
-numeric comparisons, so string comparisons are recommended.
+When comparing C<$]>, string comparison operators are B<highly
+recommended>. The inherent limitations of binary floating point
+representation can sometimes lead to incorrect comparisons for some
+numbers on some architectures.
See also the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
+See L</$^V> for a representation of the Perl version as a L<version>
+object, which allows more flexible string comparisons.
+
+The main advantage of C<$]> over C<$^V> is that it works the same on any
+version of Perl. The disadvantages are that it can't easily be compared
+to versions in other formats (e.g. literal v-strings, "v1.2.3" or
+version objects) and numeric comparisons can occasionally fail; it's good
+for string literal version checks and bad for comparing to a variable
+that hasn't been sanity-checked.
+
Mnemonic: Is this version of perl in the right bracket?
=back
https://perl5.git.perl.org / perl5.git / blobdiff