strict(3pm) [mojave man page]

strict(3pm)						 Perl Programmers Reference Guide					       strict(3pm)

NAME

       strict - Perl pragma to restrict unsafe constructs

SYNOPSIS

	   use strict;

	   use strict "vars";
	   use strict "refs";
	   use strict "subs";

	   use strict;
	   no strict "vars";

DESCRIPTION

       If no import list is supplied, all possible restrictions are assumed.  (This is the safest mode to operate in, but is sometimes too strict
       for casual programming.)  Currently, there are three possible things to be strict about:  "subs", "vars", and "refs".

       "strict refs"
	     This generates a runtime error if you use symbolic references (see perlref).

		 use strict 'refs';
		 $ref = $foo;
		 print $$ref;	     # ok
		 $ref = "foo";
		 print $$ref;	     # runtime error; normally ok
		 $file = "STDOUT";
		 print $file "Hi!";  # error; note: no comma after $file

	     There is one exception to this rule:

		 $bar = &{'foo'};
		 &$bar;

	     is allowed so that "goto &$AUTOLOAD" would not break under stricture.

       "strict vars"
	     This generates a compile-time error if you access a variable that was neither explicitly declared (using any of "my", "our", "state",
	     or "use vars") nor fully qualified.  (Because this is to avoid variable suicide problems and subtle dynamic scoping issues, a merely
	     "local" variable isn't good enough.)  See "my" in perlfunc, "our" in perlfunc, "state" in perlfunc, "local" in perlfunc, and vars.

		 use strict 'vars';
		 $X::foo = 1;	      # ok, fully qualified
		 my $foo = 10;	      # ok, my() var
		 local $baz = 9;      # blows up, $baz not declared before

		 package Cinna;
		 our $bar;		     # Declares $bar in current package
		 $bar = 'HgS';		     # ok, global declared via pragma

	     The local() generated a compile-time error because you just touched a global name without fully qualifying it.

	     Because of their special use by sort(), the variables $a and $b are exempted from this check.

       "strict subs"
	     This disables the poetry optimization, generating a compile-time error if you try to use a bareword identifier that's not a
	     subroutine, unless it is a simple identifier (no colons) and that it appears in curly braces or on the left hand side of the "=>"
	     symbol.

		 use strict 'subs';
		 $SIG{PIPE} = Plumber;	     # blows up
		 $SIG{PIPE} = "Plumber";     # just fine: quoted string is always ok
		 $SIG{PIPE} = &Plumber;     # preferred form

       See "Pragmatic Modules" in perlmodlib.

HISTORY

       "strict 'subs'", with Perl 5.6.1, erroneously permitted to use an unquoted compound identifier (e.g. "Foo::Bar") as a hash key (before "=>"
       or inside curlies), but without forcing it always to a literal string.

       Starting with Perl 5.8.1 strict is strict about its restrictions: if unknown restrictions are used, the strict pragma will abort with

	   Unknown 'strict' tag(s) '...'

       As of version 1.04 (Perl 5.10), strict verifies that it is used as "strict" to avoid the dreaded Strict trap on case insensitive file
       systems.

perl v5.18.2							    2014-01-06							       strict(3pm)

Check Out this Related Man Page

Symbol(3pm)						 Perl Programmers Reference Guide					       Symbol(3pm)

NAME

       Symbol - manipulate Perl symbols and their names

SYNOPSIS

	   use Symbol;

	   $sym = gensym;
	   open($sym, "filename");
	   $_ = <$sym>;
	   # etc.

	   ungensym $sym;      # no effect

	   # replace *FOO{IO} handle but not $FOO, %FOO, etc.
	   *FOO = geniosym;

	   print qualify("x"), "
";		  # "main::x"
	   print qualify("x", "FOO"), "
";	  # "FOO::x"
	   print qualify("BAR::x"), "
";	  # "BAR::x"
	   print qualify("BAR::x", "FOO"), "
";  # "BAR::x"
	   print qualify("STDOUT", "FOO"), "
";  # "main::STDOUT" (global)
	   print qualify(*x), "
";		  # returns *x
	   print qualify(*x, "FOO"), "
";	  # returns *x

	   use strict refs;
	   print { qualify_to_ref $fh } "foo!
";
	   $ref = qualify_to_ref $name, $pkg;

	   use Symbol qw(delete_package);
	   delete_package('Foo::Bar');
	   print "deleted
" unless exists $Foo::{'Bar::'};

DESCRIPTION

       "Symbol::gensym" creates an anonymous glob and returns a reference to it.  Such a glob reference can be used as a file or directory handle.

       For backward compatibility with older implementations that didn't support anonymous globs, "Symbol::ungensym" is also provided.	But it
       doesn't do anything.

       "Symbol::geniosym" creates an anonymous IO handle.  This can be assigned into an existing glob without affecting the non-IO portions of the
       glob.

       "Symbol::qualify" turns unqualified symbol names into qualified variable names (e.g. "myvar" -> "MyPackage::myvar").  If it is given a
       second parameter, "qualify" uses it as the default package; otherwise, it uses the package of its caller.  Regardless, global variable
       names (e.g. "STDOUT", "ENV", "SIG") are always qualified with "main::".

       Qualification applies only to symbol names (strings).  References are left unchanged under the assumption that they are glob references,
       which are qualified by their nature.

       "Symbol::qualify_to_ref" is just like "Symbol::qualify" except that it returns a glob ref rather than a symbol name, so you can use the
       result even if "use strict 'refs'" is in effect.

       "Symbol::delete_package" wipes out a whole package namespace.  Note this routine is not exported by default--you may want to import it
       explicitly.

BUGS

       "Symbol::delete_package" is a bit too powerful. It undefines every symbol that lives in the specified package. Since perl, for performance
       reasons, does not perform a symbol table lookup each time a function is called or a global variable is accessed, some code that has already
       been loaded and that makes use of symbols in package "Foo" may stop working after you delete "Foo", even if you reload the "Foo" module
       afterwards.

perl v5.18.2							    2013-11-04							       Symbol(3pm)

Linux and UNIX Man Pages

strict(3pm) [mojave man page]

Check Out this Related Man Page