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diff --git a/Changes5.000 b/Changes5.000 new file mode 100644 index 0000000000..78cab26f14 --- /dev/null +++ b/Changes5.000 @@ -0,0 +1,185 @@ +------------- +Version 5.000 +------------- + +New things +---------- + The -w switch is much more informative. + + References. See t/op/ref.t for examples. All entities in Perl 5 are + reference counted so that it knows when each item should be destroyed. + + Objects. See t/op/ref.t for examples. + + => is now a synonym for comma. This is useful as documentation for + arguments that come in pairs, such as initializers for associative arrays, + or named arguments to a subroutine. + + All functions have been turned into list operators or unary operators, + meaning the parens are optional. Even subroutines may be called as + list operators if they've already been declared. + + More embeddible. See main.c and embed_h.sh. Multiple interpreters + in the same process are supported (though not with interleaved + execution yet). + + The interpreter is now flattened out. Compare Perl 4's eval.c with + the perl 5's pp.c. Compare Perl 4's 900 line interpreter loop in cmd.c + with Perl 5's 1 line interpreter loop in run.c. Eventually we'll make + everything non-blocking so we can interface nicely with a scheduler. + + eval is now treated more like a subroutine call. Among other things, + this means you can return from it. + + Format value lists may be spread over multiple lines by enclosing in + a do {} block. + + You may now define BEGIN and END subroutines for each package. The BEGIN + subroutine executes the moment it's parsed. The END subroutine executes + just before exiting. + + Flags on the #! line are interpreted even if the script wasn't + executed directly. (And even if the script was located by "perl -x"!) + + The ?: operator is now legal as an lvalue. + + List context now propagates to the right side of && and ||, as well + as the 2nd and 3rd arguments to ?:. + + The "defined" function can now take a general expression. + + Lexical scoping available via "my". eval can see the current lexical + variables. + + The preferred package delimiter is now :: rather than '. + + tie/untie are now preferred to dbmopen/dbmclose. Multiple DBM + implementations are allowed in the same executable, so you can + write scripts to interchange data among different formats. + + New "and" and "or" operators work just like && and || but with + a precedence lower than comma, so they work better with list operators. + + New functions include: abs(), chr(), uc(), ucfirst(), lc(), lcfirst(), + chomp(), glob() + + require with a number checks to see that the version of Perl that is + currently running is at least that number. + + Dynamic loading of external modules is now supported. + + There is a new quote form qw//, which is equivalent to split(' ', q//). + + Assignment of a reference to a glob value now just replaces the + single element of the glob corresponding to the reference type: + *foo = \$bar, *foo = \&bletch; + + Filehandle methods are now supported: + output_autoflush STDOUT 1; + + There is now an "English" module that provides human readable translations + for cryptic variable names. + + Autoload stubs can now call the replacement subroutine with goto &realsub. + + Subroutines can be defined lazily in any package by declaring an AUTOLOAD + routine, which will be called if a non-existent subroutine is called in + that package. + + Several previously added features have been subsumed under the new + keywords "use" and "no". Saying "use Module LIST" is short for + BEGIN { require Module; import Module LIST; } + The "no" keyword is identical except that it calls "unimport" instead. + The earlier pragma mechanism now uses this mechanism, and two new + modules have been added to the library to implement "use integer" + and variations of "use strict vars, refs, subs". + + Variables may now be interpolated literally into a pattern by prefixing + them with \Q, which works just like \U, but backwhacks non-alphanumerics + instead. There is also a corresponding quotemeta function. + + Any quantifier in a regular expression may now be followed by a ? to + indicate that the pattern is supposed to match as little as possible. + + Pattern matches may now be followed by an m or s modifier to explicitly + request multiline or singleline semantics. An s modifier makes . match + newline. + + Patterns may now contain \A to match only at the beginning of the string, + and \Z to match only at the end. These differ from ^ and $ in that + they ignore multiline semantics. In addition, \G matches where the + last interation of m//g or s///g left off. + + Non-backreference-producing parens of various sorts may now be + indicated by placing a ? directly after the opening parenthesis, + followed by a character that indicates the purpose of the parens. + An :, for instance, indicates simple grouping. (?:a|b|c) will + match any of a, b or c without producing a backreference. It does + "eat" the input. There are also assertions which do not eat the + input but do lookahead for you. (?=stuff) indicates that the next + thing must be "stuff". (?!nonsense) indicates that the next thing + must not be "nonsense". + + The negation operator now treats non-numeric strings specially. + A -"text" is turned into "-text", so that -bareword is the same + as "-bareword". If the string already begins with a + or -, it + is flipped to the other sign. + +Incompatibilities +----------------- + @ now always interpolates an array in double-quotish strings. Some programs + may now need to use backslash to protect any @ that shouldn't interpolate. + + Ordinary variables starting with underscore are no longer forced into + package main. + + s'$lhs'$rhs' now does no interpolation on either side. It used to + interplolate $lhs but not $rhs. + + The second and third arguments of splice are now evaluated in scalar + context (like the book says) rather than list context. + + Saying "shift @foo + 20" is now a semantic error because of precedence. + + "open FOO || die" is now incorrect. You need parens around the filehandle. + + The elements of argument lists for formats are now evaluated in list + context. This means you can interpolate list values now. + + You can't do a goto into a block that is optimized away. Darn. + + It is no longer syntactically legal to use whitespace as the name + of a variable, or as a delimiter for any kind of quote construct. + + Some error messages will be different. + + The caller function now returns a false value in a scalar context if there + is no caller. This lets library files determine if they're being required. + + m//g now attaches its state to the searched string rather than the + regular expression. + + "reverse" is no longer allowed as the name of a sort subroutine. + + taintperl is no longer a separate executable. There is now a -T + switch to turn on tainting when it isn't turned on automatically. + + Symbols starting with _ are no longer forced into package main, except + for $_ itself (and @_, etc.). + + Double-quoted strings may no longer end with an unescaped $ or @. + + Negative array subscripts now count from the end of the array. + + The comma operator in a scalar context is now guaranteed to give a + scalar context to its arguments. + + The ** operator now binds more tightly than unary minus. + + Setting $#array lower now discards array elements so that destructors + work reasonably. + + delete is not guaranteed to return the old value for tied arrays, + since this capability may be onerous for some modules to implement. + + Attempts to set $1 through $9 now result in a run-time error. |