3 The -w switch is much more informative.
5 References. See t/op/ref.t for examples. All entities in Perl 5 are
6 reference counted so that it knows when each item should be destroyed.
8 Objects. See t/op/ref.t for examples.
10 => is now a synonym for comma. This is useful as documentation for
11 arguments that come in pairs, such as initializers for associative arrays,
12 or named arguments to a subroutine.
14 All functions have been turned into list operators or unary operators,
15 meaning the parens are optional. Even subroutines may be called as
16 list operators if they've already been declared.
18 More embeddible. See main.c and embed_h.SH. Multiple interpreters
19 in the same process are supported (though not with interleaved
22 The interpreter is now flattened out. Compare Perl 4's eval.c with
23 the perl 5's pp.c. Compare Perl 4's 900 line interpreter loop in cmd.c
24 with Perl 5's 1 line interpreter loop in run.c. Eventually we'll make
25 everything non-blocking so we can interface nicely with a scheduler.
27 eval is now treated more like a subroutine call. Among other things,
28 this means you can return from it.
30 Format value lists may be spread over multiple lines by enclosing in
33 You may now define BEGIN and END subroutines for each package. The BEGIN
34 subroutine executes the moment it's parsed. The END subroutine executes
37 Flags on the #! line are interpreted even if the script wasn't
38 executed directly. (And even if the script was located by "perl -x"!)
40 The ?: operator is now legal as an lvalue.
42 List context now propagates to the right side of && and ||, as well
43 as the 2nd and 3rd arguments to ?:.
45 The "defined" function can now take a general expression.
47 Lexical scoping available via "my". eval can see the current lexical
50 Saying "package;" requires explicit package name on global symbols.
52 The preferred package delimiter is now :: rather than '.
54 tie/untie are now preferred to dbmopen/dbmclose. Multiple DBM
55 implementations are allowed in the same executable, so you can
56 write scripts to interchange data among different formats.
58 New "and" and "or" operators work just like && and || but with
59 a precedence lower than comma, so they work better with list operators.
61 New functions include: abs(), chr(), uc(), ucfirst(), lc(), lcfirst()
63 require with a bare word now does an immediate require at compile time.
64 So "require POSIX" is equivalent to "BEGIN { require 'POSIX.pm' }".
66 require with a number checks to see that the version of Perl that is
67 currently running is at least that number.
69 Dynamic loading of external modules is now supported.
71 There is a new quote form qw//, which is equivalent to split(' ', q//).
73 Assignment of a reference to a glob value now just replaces the
74 single element of the glob corresponding to the reference type:
75 *foo = \$bar, *foo = \&bletch;
77 Filehandle methods are now supported:
78 output_autoflush STDOUT 1;
80 There is now an "English" module that provides human readable translations
81 for cryptic variable names.
83 Autoload stubs can now call the replacement subroutine with goto &realsub.
85 Subroutines can be defined lazily in any package by declaring an AUTOLOAD
86 routine, which will be called if a non-existent subroutine is called in
91 @ now always interpolates an array in double-quotish strings. Some programs
92 may now need to use backslash to protect any @ that shouldn't interpolate.
94 s'$lhs'$rhs' now does no interpolation on either side. It used to
95 interplolate $lhs but not $rhs.
97 The second and third arguments of splice are now evaluated in scalar
98 context (like the book says) rather than list context.
100 Saying "shift @foo + 20" is now a semantic error because of precedence.
102 "open FOO || die" is now incorrect. You need parens around the filehandle.
104 The elements of argument lists for formats are now evaluated in list
105 context. This means you can interpolate list values now.
107 You can't do a goto into a block that is optimized away. Darn.
109 It is no longer syntactically legal to use whitespace as the name
112 Some error messages will be different.
114 The caller function now returns a false value in a scalar context if there
115 is no caller. This lets library files determine if they're being required.
117 m//g now attaches its state to the searched string rather than the
120 "reverse" is no longer allowed as the name of a sort subroutine.
122 taintperl is no longer a separate executable. There is now a -T
123 switch to turn on tainting when it isn't turned on automatically.
125 Symbols starting with _ are no longer forced into package main, except
126 for $_ itself (and @_, etc.).
128 Double-quoted strings may no longer end with an unescaped $ or @.
130 Negative array subscripts now count from the end of the array.
132 The comma operator in a scalar context is now guaranteed to give a
133 scalar context to its arguments.