function without an explicit return statement is called a subroutine, but
there's really no difference from the language's perspective.)
-Any arguments passed to the routine come in as the array @_. Thus if you
+Any arguments passed to the routine come in as the array C<@_>. Thus if you
called a function with two arguments, those would be stored in C<$_[0]>
-and C<$_[1]>. The array @_ is a local array, but its elements are
+and C<$_[1]>. The array C<@_> is a local array, but its elements are
aliases for the actual scalar parameters. In particular, if an element
C<$_[0]> is updated, the corresponding argument is updated (or an error
occurs if it is not updatable). If an argument is an array or hash
element which did not exist when the function was called, that element is
created only when (and if) it is modified or if a reference to it is
taken. (Some earlier versions of Perl created the element whether or not
-it was assigned to.) Note that assigning to the whole array @_ removes
+it was assigned to.) Note that assigning to the whole array C<@_> removes
the aliasing, and does not update any arguments.
The return value of the subroutine is the value of the last expression
-evaluated. Alternatively, a return statement may be used to exit the
+evaluated. Alternatively, a C<return> statement may be used to exit the
subroutine, optionally specifying the returned value, which will be
evaluated in the appropriate context (list, scalar, or void) depending
on the context of the subroutine call. If you specify no return value,
one large indistinguishable list.
Perl does not have named formal parameters, but in practice all you do is
-assign to a my() list of these. Any variables you use in the function
+assign to a C<my()> list of these. Any variables you use in the function
that aren't declared private are global variables. For the gory details
on creating private variables, see
L<"Private Variables via my()"> and L<"Temporary Values via local()">.
This also has the effect of turning call-by-reference into call-by-value,
because the assignment copies the values. Otherwise a function is free to
-do in-place modifications of @_ and change its caller's values.
+do in-place modifications of C<@_> and change its caller's values.
upcase_in($v1, $v2); # this changes $v1 and $v2
sub upcase_in {
upcase_in("frederick");
-It would be much safer if the upcase_in() function
+It would be much safer if the C<upcase_in()> function
were written to return a copy of its parameters instead
of changing them in place:
}
Notice how this (unprototyped) function doesn't care whether it was passed
-real scalars or arrays. Perl will see everything as one big long flat @_
+real scalars or arrays. Perl will see everything as one big long flat C<@_>
parameter list. This is one of the ways where Perl's simple
-argument-passing style shines. The upcase() function would work perfectly
-well without changing the upcase() definition even if we fed it things
+argument-passing style shines. The C<upcase()> function would work perfectly
+well without changing the C<upcase()> definition even if we fed it things
like this:
@newlist = upcase(@list1, @list2);
(@a, @b) = upcase(@list1, @list2);
Because like its flat incoming parameter list, the return list is also
-flat. So all you have managed to do here is stored everything in @a and
-made @b an empty list. See L<Pass by Reference> for alternatives.
+flat. So all you have managed to do here is stored everything in C<@a> and
+made C<@b> an empty list. See L<Pass by Reference> for alternatives.
-A subroutine may be called using the "&" prefix. The "&" is optional
+A subroutine may be called using the "C<&>" prefix. The "C<&>" is optional
in modern Perls, and so are the parentheses if the subroutine has been
-predeclared. (Note, however, that the "&" is I<NOT> optional when
+predeclared. (Note, however, that the "C<&>" is I<NOT> optional when
you're just naming the subroutine, such as when it's used as an
-argument to defined() or undef(). Nor is it optional when you want to
+argument to C<defined()> or C<undef()>. Nor is it optional when you want to
do an indirect subroutine call with a subroutine name or reference
using the C<&$subref()> or C<&{$subref}()> constructs. See L<perlref>
for more on that.)
Subroutines may be called recursively. If a subroutine is called using
-the "&" form, the argument list is optional, and if omitted, no @_ array is
-set up for the subroutine: the @_ array at the time of the call is
+the "C<&>" form, the argument list is optional, and if omitted, no C<@_> array is
+set up for the subroutine: the C<@_> array at the time of the call is
visible to subroutine instead. This is an efficiency mechanism that
new users may wish to avoid.
&foo; # foo() get current args, like foo(@_) !!
foo; # like foo() IFF sub foo predeclared, else "foo"
-Not only does the "&" form make the argument list optional, but it also
+Not only does the "C<&>" form make the argument list optional, but it also
disables any prototype checking on the arguments you do provide. This
is partly for historical reasons, and partly for having a convenient way
to cheat if you know what you're doing. See the section on Prototypes below.
just as are modules whose names are in all lower case. A function in
all capitals is a loosely-held convention meaning it will be called
indirectly by the run-time system itself. Functions that do special,
-pre-defined things BEGIN, END, AUTOLOAD, and DESTROY--plus all the
-functions mentioned in L<perltie>. The 5.005 release adds INIT
+pre-defined things are C<BEGIN>, C<END>, C<AUTOLOAD>, and C<DESTROY>--plus all the
+functions mentioned in L<perltie>. The 5.005 release adds C<INIT>
to this list.
-=head2 Private Variables via my()
+=head2 Private Variables via C<my()>
Synopsis:
my $foo = "flurp"; # declare $foo lexical, and init it
my @oof = @bar; # declare @oof lexical, and init it
-A "my" declares the listed variables to be confined (lexically) to the
+A "C<my>" declares the listed variables to be confined (lexically) to the
enclosing block, conditional (C<if/unless/elsif/else>), loop
(C<for/foreach/while/until/continue>), subroutine, C<eval>, or
C<do/require/use>'d file. If more than one value is listed, the list
must be placed in parentheses. All listed elements must be legal lvalues.
Only alphanumeric identifiers may be lexically scoped--magical
-builtins like $/ must currently be localized with "local" instead.
+builtins like C<$/> must currently be C<local>ize with "C<local>" instead.
-Unlike dynamic variables created by the "local" operator, lexical
-variables declared with "my" are totally hidden from the outside world,
+Unlike dynamic variables created by the "C<local>" operator, lexical
+variables declared with "C<my>" are totally hidden from the outside world,
including any called subroutines (even if it's the same subroutine called
from itself or elsewhere--every call gets its own copy).
-This doesn't mean that a my() variable declared in a statically
+This doesn't mean that a C<my()> variable declared in a statically
I<enclosing> lexical scope would be invisible. Only the dynamic scopes
-are cut off. For example, the bumpx() function below has access to the
-lexical $x variable because both the my and the sub occurred at the same
+are cut off. For example, the C<bumpx()> function below has access to the
+lexical C<$x> variable because both the my and the sub occurred at the same
scope, presumably the file scope.
my $x = 10;
sub bumpx { $x++ }
-(An eval(), however, can see the lexical variables of the scope it is
+(An C<eval()>, however, can see the lexical variables of the scope it is
being evaluated in so long as the names aren't hidden by declarations within
-the eval() itself. See L<perlref>.)
+the C<eval()> itself. See L<perlref>.)
-The parameter list to my() may be assigned to if desired, which allows you
+The parameter list to C<my()> may be assigned to if desired, which allows you
to initialize your variables. (If no initializer is given for a
particular variable, it is created with the undefined value.) Commonly
this is used to name the parameters to a subroutine. Examples:
return $arg;
}
-The "my" is simply a modifier on something you might assign to. So when
-you do assign to the variables in its argument list, the "my" doesn't
+The "C<my>" is simply a modifier on something you might assign to. So when
+you do assign to the variables in its argument list, the "C<my>" doesn't
change whether those variables are viewed as a scalar or an array. So
my ($foo) = <STDIN>; # WRONG?
my $x = $x;
-can be used to initialize the new $x with the value of the old $x, and
+can be used to initialize the new $x with the value of the old C<$x>, and
the expression
my $x = 123 and $x == 123
-is false unless the old $x happened to have the value 123.
+is false unless the old C<$x> happened to have the value C<123>.
Lexical scopes of control structures are not bounded precisely by the
braces that delimit their controlled blocks; control expressions are
print $line;
}
-the scope of $line extends from its declaration throughout the rest of
+the scope of C<$line> extends from its declaration throughout the rest of
the loop construct (including the C<continue> clause), but not beyond
it. Similarly, in the conditional
die "'$answer' is neither 'yes' nor 'no'";
}
-the scope of $answer extends from its declaration throughout the rest
+the scope of C<$answer> extends from its declaration throughout the rest
of the conditional (including C<elsif> and C<else> clauses, if any),
but not beyond it.
The C<foreach> loop defaults to scoping its index variable dynamically
(in the manner of C<local>; see below). However, if the index
-variable is prefixed with the keyword "my", then it is lexically
+variable is prefixed with the keyword "C<my>", then it is lexically
scoped instead. Thus in the loop
for my $i (1, 2, 3) {
some_function();
}
-the scope of $i extends to the end of the loop, but not beyond it, and
-so the value of $i is unavailable in some_function().
+the scope of C<$i> extends to the end of the loop, but not beyond it, and
+so the value of C<$i> is unavailable in C<some_function()>.
Some users may wish to encourage the use of lexically scoped variables.
As an aid to catching implicit references to package variables,
then any variable reference from there to the end of the enclosing
block must either refer to a lexical variable, or must be fully
qualified with the package name. A compilation error results
-otherwise. An inner block may countermand this with S<"no strict 'vars'">.
+otherwise. An inner block may countermand this with S<"C<no strict 'vars'>">.
-A my() has both a compile-time and a run-time effect. At compile time,
+A C<my()> has both a compile-time and a run-time effect. At compile time,
the compiler takes notice of it; the principle usefulness of this is to
-quiet C<use strict 'vars'>. The actual initialization is delayed until
+quiet S<"C<use strict 'vars'>">. The actual initialization is delayed until
run time, so it gets executed appropriately; every time through a loop,
for example.
-Variables declared with "my" are not part of any package and are therefore
+Variables declared with "C<my>" are not part of any package and are therefore
never fully qualified with the package name. In particular, you're not
allowed to try to make a package variable (or other global) lexical:
my $_; # also illegal (currently)
In fact, a dynamic variable (also known as package or global variables)
-are still accessible using the fully qualified :: notation even while a
+are still accessible using the fully qualified C<::> notation even while a
lexical of the same name is also visible:
package main;
my $x = 20;
print "$x and $::x\n";
-That will print out 20 and 10.
+That will print out C<20> and C<10>.
-You may declare "my" variables at the outermost scope of a file to hide
+You may declare "C<my>" variables at the outermost scope of a file to hide
any such identifiers totally from the outside world. This is similar
to C's static variables at the file level. To do this with a subroutine
requires the use of a closure (anonymous function with lexical access).
-If a block (such as an eval(), function, or C<package>) wants to create
+If a block (such as an C<eval()>, function, or C<package>) wants to create
a private subroutine that cannot be called from outside that block,
it can declare a lexical variable containing an anonymous sub reference:
As long as the reference is never returned by any function within the
module, no outside module can see the subroutine, because its name is not in
any package's symbol table. Remember that it's not I<REALLY> called
-$some_pack::secret_version or anything; it's just $secret_version,
+C<$some_pack::secret_version> or anything; it's just C<$secret_version>,
unqualified and unqualifiable.
This does not work with object methods, however; all object methods have
=head2 Peristent Private Variables
Just because a lexical variable is lexically (also called statically)
-scoped to its enclosing block, eval, or do FILE, this doesn't mean that
+scoped to its enclosing block, C<eval>, or C<do> FILE, this doesn't mean that
within a function it works like a C static. It normally works more
like a C auto, but with implicit garbage collection.
If this function is being sourced in from a separate file
via C<require> or C<use>, then this is probably just fine. If it's
-all in the main program, you'll need to arrange for the my()
+all in the main program, you'll need to arrange for the C<my()>
to be executed early, either by putting the whole block above
-your main program, or more likely, placing merely a BEGIN
+your main program, or more likely, placing merely a C<BEGIN>
sub around it to make sure it gets executed before your program
starts to run:
}
}
-See L<perlrun> about the BEGIN function.
+See L<perlmod/"Package Constructors and Destructors"> about the C<BEGIN> function.
If declared at the outermost scope, the file scope, then lexicals work
someone like C's file statics. They are available to all functions in
=head2 Temporary Values via local()
-B<NOTE>: In general, you should be using "my" instead of "local", because
+B<NOTE>: In general, you should be using "C<my>" instead of "C<local>", because
it's faster and safer. Exceptions to this include the global punctuation
variables, filehandles and formats, and direct manipulation of the Perl
-symbol table itself. Format variables often use "local" though, as do
+symbol table itself. Format variables often use "C<local>" though, as do
other variables whose current value must be visible to called
subroutines.
local *merlyn = 'randal'; # SAME THING: promote 'randal' to *randal
local *merlyn = \$randal; # just alias $merlyn, not @merlyn etc
-A local() modifies its listed variables to be "local" to the enclosing
-block, eval, or C<do FILE>--and to I<any called from within that block>.
-A local() just gives temporary values to global (meaning package)
-variables. It does not create a local variable. This is known as
-dynamic scoping. Lexical scoping is done with "my", which works more
+A C<local()> modifies its listed variables to be "local" to the enclosing
+block, C<eval>, or C<do FILE>--and to I<any subroutine called from within that block>.
+A C<local()> just gives temporary values to global (meaning package)
+variables. It does B<not> create a local variable. This is known as
+dynamic scoping. Lexical scoping is done with "C<my>", which works more
like C's auto declarations.
-If more than one variable is given to local(), they must be placed in
+If more than one variable is given to C<local()>, they must be placed in
parentheses. All listed elements must be legal lvalues. This operator works
by saving the current values of those variables in its argument list on a
hidden stack and restoring them upon exiting the block, subroutine, or
}
# old %digits restored here
-Because local() is a run-time command, it gets executed every time
+Because C<local()> is a run-time command, it gets executed every time
through a loop. In releases of Perl previous to 5.0, this used more stack
storage each time until the loop was exited. Perl now reclaims the space
each time through, but it's still more efficient to declare your variables
outside the loop.
-A local is simply a modifier on an lvalue expression. When you assign to
-a localized variable, the local doesn't change whether its list is viewed
+A C<local> is simply a modifier on an lvalue expression. When you assign to
+a C<local>ized variable, the C<local> doesn't change whether its list is viewed
as a scalar or an array. So
local($foo) = <STDIN>;
[..normal %ENV behavior here..]
It's also worth taking a moment to explain what happens when you
-localize a member of a composite type (i.e. an array or hash element).
-In this case, the element is localized I<by name>. This means that
+C<local>ize a member of a composite type (i.e. an array or hash element).
+In this case, the element is C<local>ized I<by name>. This means that
when the scope of the C<local()> ends, the saved value will be
restored to the hash element whose key was named in the C<local()>, or
the array element whose index was named in the C<local()>. If that
When evaluated, the typeglob produces a scalar value that represents
all the objects of that name, including any filehandle, format, or
subroutine. When assigned to, it causes the name mentioned to refer to
-whatever "*" value was assigned to it. Example:
+whatever "C<*>" value was assigned to it. Example:
sub doubleary {
local(*someary) = @_;
Note that scalars are already passed by reference, so you can modify
scalar arguments without using this mechanism by referring explicitly
to C<$_[0]> etc. You can modify all the elements of an array by passing
-all the elements as scalars, but you have to use the * mechanism (or
-the equivalent reference mechanism) to push, pop, or change the size of
+all the elements as scalars, but you have to use the C<*> mechanism (or
+the equivalent reference mechanism) to C<push>, C<pop>, or change the size of
an array. It will certainly be faster to pass the typeglob (or reference).
Even if you don't want to modify an array, this mechanism is useful for
=head2 When to Still Use local()
-Despite the existence of my(), there are still three places where the
-local() operator still shines. In fact, in these three places, you
+Despite the existence of C<my()>, there are still three places where the
+C<local()> operator still shines. In fact, in these three places, you
I<must> use C<local> instead of C<my>.
=over
-=item 1. You need to give a global variable a temporary value, especially $_.
+=item 1. You need to give a global variable a temporary value, especially C<$_>.
-The global variables, like @ARGV or the punctuation variables, must be
-localized with local(). This block reads in I</etc/motd>, and splits
+The global variables, like C<@ARGV> or the punctuation variables, must be
+C<local>ized with C<local()>. This block reads in F</etc/motd>, and splits
it up into chunks separated by lines of equal signs, which are placed
-in @Fields.
+in C<@Fields>.
{
local @ARGV = ("/etc/motd");
@Fields = split /^\s*=+\s*$/;
}
-It particular, its important to localize $_ in any routine that assigns
+It particular, it's important to C<local>ize C<$_> in any routine that assigns
to it. Look out for implicit assignments in C<while> conditionals.
=item 2. You need to create a local file or directory handle or a local function.
-A function that needs a filehandle of its own must use local() uses
-local() on complete typeglob. This can be used to create new symbol
+A function that needs a filehandle of its own must use C<local()> uses
+C<local()> on complete typeglob. This can be used to create new symbol
table entries:
sub ioqueue {
a local alias.
{
- local *grow = \&shrink; # only until this block exists
- grow(); # really calls shrink()
- move(); # if move() grow()s, it shrink()s too
+ local *grow = \&shrink; # only until this block exists
+ grow(); # really calls shrink()
+ move(); # if move() grow()s, it shrink()s too
}
- grow(); # get the real grow() again
+ grow(); # get the real grow() again
See L<perlref/"Function Templates"> for more about manipulating
functions by name in this way.
=item 3. You want to temporarily change just one element of an array or hash.
-You can localize just one element of an aggregate. Usually this
+You can C<local>ize just one element of an aggregate. Usually this
is done on dynamics:
{
This section may not make much sense to you otherwise.
Here are a few simple examples. First, let's pass in several
-arrays to a function and have it pop all of then, return a new
+arrays to a function and have it C<pop> all of then, return a new
list of all their former last elements:
@tailings = popmany ( \@a, \@b, \@c, \@d );
or
(%a, %b) = func(%c, %d);
-That syntax simply won't work. It sets just @a or %a and clears the @b or
-%b. Plus the function didn't get passed into two separate arrays or
-hashes: it got one long list in @_, as always.
+That syntax simply won't work. It sets just C<@a> or C<%a> and clears the C<@b> or
+C<%b>. Plus the function didn't get passed into two separate arrays or
+hashes: it got one long list in C<@_>, as always.
If you can arrange for everyone to deal with this through references, it's
cleaner code, although not so nice to look at. Here's a function that
}
Here we're using the typeglobs to do symbol table aliasing. It's
-a tad subtle, though, and also won't work if you're using my()
-variables, because only globals (well, and local()s) are in the symbol table.
+a tad subtle, though, and also won't work if you're using C<my()>
+variables, because only globals (well, and C<local()>s) are in the symbol table.
If you're passing around filehandles, you could usually just use the bare
-typeglob, like *STDOUT, but typeglobs references would be better because
-they'll still work properly under C<use strict 'refs'>. For example:
+typeglob, like C<*STDOUT>, but typeglobs references would be better because
+they'll still work properly under S<C<use strict 'refs'>>. For example:
splutter(\*STDOUT);
sub splutter {
return scalar <$fh>;
}
-Another way to do this is using *HANDLE{IO}, see L<perlref> for usage
+Another way to do this is using C<*HANDLE{IO}>, see L<perlref> for usage
and caveats.
If you're planning on generating new filehandles, you could do this:
}
Although that will actually produce a small memory leak. See the bottom
-of L<perlfunc/open()> for a somewhat cleaner way using the IO::Handle
+of L<perlfunc/open()> for a somewhat cleaner way using the C<IO::Handle>
package.
=head2 Prototypes
sub mypush (\@@)
-then mypush() takes arguments exactly like push() does. The declaration
+then C<mypush()> takes arguments exactly like C<push()> does. The declaration
of the function to be called must be visible at compile time. The prototype
affects only the interpretation of new-style calls to the function, where
new-style is defined as not using the C<&> character. In other words,
Declared as Called as
- sub mylink ($$) mylink $old, $new
- sub myvec ($$$) myvec $var, $offset, 1
- sub myindex ($$;$) myindex &getstring, "substr"
- sub mysyswrite ($$$;$) mysyswrite $buf, 0, length($buf) - $off, $off
- sub myreverse (@) myreverse $a,$b,$c
- sub myjoin ($@) myjoin ":",$a,$b,$c
- sub mypop (\@) mypop @array
- sub mysplice (\@$$@) mysplice @array,@array,0,@pushme
- sub mykeys (\%) mykeys %{$hashref}
- sub myopen (*;$) myopen HANDLE, $name
- sub mypipe (**) mypipe READHANDLE, WRITEHANDLE
- sub mygrep (&@) mygrep { /foo/ } $a,$b,$c
- sub myrand ($) myrand 42
- sub mytime () mytime
+ sub mylink ($$) mylink $old, $new
+ sub myvec ($$$) myvec $var, $offset, 1
+ sub myindex ($$;$) myindex &getstring, "substr"
+ sub mysyswrite ($$$;$) mysyswrite $buf, 0, length($buf) - $off, $off
+ sub myreverse (@) myreverse $a, $b, $c
+ sub myjoin ($@) myjoin ":", $a, $b, $c
+ sub mypop (\@) mypop @array
+ sub mysplice (\@$$@) mysplice @array, @array, 0, @pushme
+ sub mykeys (\%) mykeys %{$hashref}
+ sub myopen (*;$) myopen HANDLE, $name
+ sub mypipe (**) mypipe READHANDLE, WRITEHANDLE
+ sub mygrep (&@) mygrep { /foo/ } $a, $b, $c
+ sub myrand ($) myrand 42
+ sub mytime () mytime
Any backslashed prototype character represents an actual argument
that absolutely must start with that character. The value passed
C<\> to that argument.
Unbackslashed prototype characters have special meanings. Any
-unbackslashed @ or % eats all the rest of the arguments, and forces
-list context. An argument represented by $ forces scalar context. An
-& requires an anonymous subroutine, which, if passed as the first
-argument, does not require the "sub" keyword or a subsequent comma. A
-* does whatever it has to do to turn the argument into a reference to a
+unbackslashed C<@> or C<%> eats all the rest of the arguments, and forces
+list context. An argument represented by C<$> forces scalar context. An
+C<&> requires an anonymous subroutine, which, if passed as the first
+argument, does not require the "C<sub>" keyword or a subsequent comma. A
+C<*> does whatever it has to do to turn the argument into a reference to a
symbol table entry.
A semicolon separates mandatory arguments from optional arguments.
-(It is redundant before @ or %.)
+(It is redundant before C<@> or C<%>.)
Note how the last three examples above are treated specially by the parser.
-mygrep() is parsed as a true list operator, myrand() is parsed as a
-true unary operator with unary precedence the same as rand(), and
-mytime() is truly without arguments, just like time(). That is, if you
+C<mygrep()> is parsed as a true list operator, C<myrand()> is parsed as a
+true unary operator with unary precedence the same as C<rand()>, and
+C<mytime()> is truly without arguments, just like C<time()>. That is, if you
say
mytime +2;
-you'll get mytime() + 2, not mytime(2), which is how it would be parsed
+you'll get C<mytime() + 2>, not C<mytime(2)>, which is how it would be parsed
without the prototype.
-The interesting thing about & is that you can generate new syntax with it:
+The interesting thing about C<&> is that you can generate new syntax with it:
sub try (&@) {
my($try,$catch) = @_;
/phooey/ and print "unphooey\n";
};
-That prints "unphooey". (Yes, there are still unresolved
-issues having to do with the visibility of @_. I'm ignoring that
-question for the moment. (But note that if we make @_ lexically
+That prints C<"unphooey">. (Yes, there are still unresolved
+issues having to do with the visibility of C<@_>. I'm ignoring that
+question for the moment. (But note that if we make C<@_> lexically
scoped, those anonymous subroutines can act like closures... (Gee,
is this sounding a little Lispish? (Never mind.))))
-And here's a reimplementation of grep:
+And here's a reimplementation of C<grep>:
sub mygrep (&@) {
my $code = shift;
func(@foo);
func( split /:/ );
-Then you've just supplied an automatic scalar() in front of their
-argument, which can be more than a bit surprising. The old @foo
+Then you've just supplied an automatic C<scalar()> in front of their
+argument, which can be more than a bit surprising. The old C<@foo>
which used to hold one thing doesn't get passed in. Instead,
-the func() now gets passed in 1, that is, the number of elements
-in @foo. And the split() gets called in a scalar context and
-starts scribbling on your @_ parameter list.
+the C<func()> now gets passed in C<1>, that is, the number of elements
+in C<@foo>. And the C<split()> gets called in a scalar context and
+starts scribbling on your C<@_> parameter list.
This is all very powerful, of course, and should be used only in moderation
to make the world a better place.
either a constant or a lexically-scoped scalar which has no other
references, then it will be used in place of function calls made
without C<&> or C<do>. Calls made using C<&> or C<do> are never
-inlined. (See constant.pm for an easy way to declare most
+inlined. (See F<constant.pm> for an easy way to declare most
constants.)
The following functions would all be inlined:
if the current package has imported some other subroutine called
C<&open()> from elsewhere.
-Library modules should not in general export builtin names like "open"
-or "chdir" as part of their default @EXPORT list, because these may
+Library modules should not in general export builtin names like "C<open>"
+or "C<chdir>" as part of their default C<@EXPORT> list, because these may
sneak into someone else's namespace and change the semantics unexpectedly.
-Instead, if the module adds the name to the @EXPORT_OK list, then it's
+Instead, if the module adds the name to the C<@EXPORT_OK> list, then it's
possible for a user to import the name explicitly, but not implicitly.
That is, they could say
use Module 'open';
-and it would import the open override, but if they said
+and it would import the C<open> override, but if they said
use Module;
packages that were searched for the original subroutine, then that
C<AUTOLOAD> subroutine is called with the arguments that would have been
passed to the original subroutine. The fully qualified name of the
-original subroutine magically appears in the $AUTOLOAD variable in the
+original subroutine magically appears in the C<$AUTOLOAD> variable in the
same package as the C<AUTOLOAD> routine. The name is not passed as an
ordinary argument because, er, well, just because, that's why...
without a trace. (See the standard C<AutoLoader> module, for example.)
But an C<AUTOLOAD> routine can also just emulate the routine and never
define it. For example, let's pretend that a function that wasn't defined
-should just call system() with those arguments. All you'd do is this:
+should just call C<system()> with those arguments. All you'd do is this:
sub AUTOLOAD {
my $program = $AUTOLOAD;
projects / p5sagit/p5-mst-13.2.git / blobdiff