186 lines
7.5 KiB
Plaintext
186 lines
7.5 KiB
Plaintext
-------------
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Version 5.000
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-------------
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New things
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----------
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The -w switch is much more informative.
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References. See t/op/ref.t for examples. All entities in Perl 5 are
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reference counted so that it knows when each item should be destroyed.
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Objects. See t/op/ref.t for examples.
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=> is now a synonym for comma. This is useful as documentation for
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arguments that come in pairs, such as initializers for associative arrays,
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or named arguments to a subroutine.
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All functions have been turned into list operators or unary operators,
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meaning the parens are optional. Even subroutines may be called as
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list operators if they've already been declared.
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More embeddible. See main.c and embed_h.sh. Multiple interpreters
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in the same process are supported (though not with interleaved
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execution yet).
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The interpreter is now flattened out. Compare Perl 4's eval.c with
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the perl 5's pp.c. Compare Perl 4's 900 line interpreter loop in cmd.c
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with Perl 5's 1 line interpreter loop in run.c. Eventually we'll make
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everything non-blocking so we can interface nicely with a scheduler.
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eval is now treated more like a subroutine call. Among other things,
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this means you can return from it.
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Format value lists may be spread over multiple lines by enclosing in
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a do {} block.
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You may now define BEGIN and END subroutines for each package. The BEGIN
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subroutine executes the moment it's parsed. The END subroutine executes
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just before exiting.
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Flags on the #! line are interpreted even if the script wasn't
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executed directly. (And even if the script was located by "perl -x"!)
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The ?: operator is now legal as an lvalue.
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List context now propagates to the right side of && and ||, as well
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as the 2nd and 3rd arguments to ?:.
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The "defined" function can now take a general expression.
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Lexical scoping available via "my". eval can see the current lexical
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variables.
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The preferred package delimiter is now :: rather than '.
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tie/untie are now preferred to dbmopen/dbmclose. Multiple DBM
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implementations are allowed in the same executable, so you can
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write scripts to interchange data among different formats.
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New "and" and "or" operators work just like && and || but with
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a precedence lower than comma, so they work better with list operators.
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New functions include: abs(), chr(), uc(), ucfirst(), lc(), lcfirst(),
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chomp(), glob()
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require with a number checks to see that the version of Perl that is
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currently running is at least that number.
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Dynamic loading of external modules is now supported.
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There is a new quote form qw//, which is equivalent to split(' ', q//).
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Assignment of a reference to a glob value now just replaces the
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single element of the glob corresponding to the reference type:
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*foo = \$bar, *foo = \&bletch;
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Filehandle methods are now supported:
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output_autoflush STDOUT 1;
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There is now an "English" module that provides human readable translations
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for cryptic variable names.
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Autoload stubs can now call the replacement subroutine with goto &realsub.
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Subroutines can be defined lazily in any package by declaring an AUTOLOAD
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routine, which will be called if a non-existent subroutine is called in
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that package.
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Several previously added features have been subsumed under the new
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keywords "use" and "no". Saying "use Module LIST" is short for
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BEGIN { require Module; import Module LIST; }
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The "no" keyword is identical except that it calls "unimport" instead.
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The earlier pragma mechanism now uses this mechanism, and two new
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modules have been added to the library to implement "use integer"
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and variations of "use strict vars, refs, subs".
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Variables may now be interpolated literally into a pattern by prefixing
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them with \Q, which works just like \U, but backwhacks non-alphanumerics
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instead. There is also a corresponding quotemeta function.
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Any quantifier in a regular expression may now be followed by a ? to
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indicate that the pattern is supposed to match as little as possible.
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Pattern matches may now be followed by an m or s modifier to explicitly
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request multiline or singleline semantics. An s modifier makes . match
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newline.
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Patterns may now contain \A to match only at the beginning of the string,
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and \Z to match only at the end. These differ from ^ and $ in that
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they ignore multiline semantics. In addition, \G matches where the
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last interation of m//g or s///g left off.
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Non-backreference-producing parens of various sorts may now be
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indicated by placing a ? directly after the opening parenthesis,
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followed by a character that indicates the purpose of the parens.
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An :, for instance, indicates simple grouping. (?:a|b|c) will
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match any of a, b or c without producing a backreference. It does
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"eat" the input. There are also assertions which do not eat the
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input but do lookahead for you. (?=stuff) indicates that the next
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thing must be "stuff". (?!nonsense) indicates that the next thing
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must not be "nonsense".
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The negation operator now treats non-numeric strings specially.
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A -"text" is turned into "-text", so that -bareword is the same
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as "-bareword". If the string already begins with a + or -, it
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is flipped to the other sign.
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Incompatibilities
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-----------------
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@ now always interpolates an array in double-quotish strings. Some programs
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may now need to use backslash to protect any @ that shouldn't interpolate.
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Ordinary variables starting with underscore are no longer forced into
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package main.
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s'$lhs'$rhs' now does no interpolation on either side. It used to
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interplolate $lhs but not $rhs.
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The second and third arguments of splice are now evaluated in scalar
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context (like the book says) rather than list context.
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Saying "shift @foo + 20" is now a semantic error because of precedence.
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"open FOO || die" is now incorrect. You need parens around the filehandle.
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The elements of argument lists for formats are now evaluated in list
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context. This means you can interpolate list values now.
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You can't do a goto into a block that is optimized away. Darn.
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It is no longer syntactically legal to use whitespace as the name
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of a variable, or as a delimiter for any kind of quote construct.
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Some error messages will be different.
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The caller function now returns a false value in a scalar context if there
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is no caller. This lets library files determine if they're being required.
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m//g now attaches its state to the searched string rather than the
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regular expression.
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"reverse" is no longer allowed as the name of a sort subroutine.
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taintperl is no longer a separate executable. There is now a -T
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switch to turn on tainting when it isn't turned on automatically.
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Symbols starting with _ are no longer forced into package main, except
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for $_ itself (and @_, etc.).
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Double-quoted strings may no longer end with an unescaped $ or @.
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Negative array subscripts now count from the end of the array.
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The comma operator in a scalar context is now guaranteed to give a
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scalar context to its arguments.
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The ** operator now binds more tightly than unary minus.
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Setting $#array lower now discards array elements so that destructors
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work reasonably.
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delete is not guaranteed to return the old value for tied arrays,
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since this capability may be onerous for some modules to implement.
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Attempts to set $1 through $9 now result in a run-time error.
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