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.\" ========================================================================
.TH strict 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide"
strict \- Perl pragma to restrict unsafe constructs
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: \*(L"subs\*(R", \*(L"vars\*(R", and \*(L"refs\*(R".
.ie n .IP """strict refs""" 6
.el .IP "\f(CWstrict refs\fR" 6
This generates a runtime error if you
use symbolic references (see perlref).
\& print $$ref; # runtime error; normally ok
\& print $file "Hi!"; # error; note: no comma after $file
There is one exception to this rule:
is allowed so that \f(CW\*(C`goto &$AUTOLOAD\*(C'\fR would not break under stricture.
.ie n .IP """strict vars""" 6
.el .IP "\f(CWstrict vars\fR" 6
This generates a compile-time error if you access a variable that wasn't
declared via \f(CW\*(C`our\*(C'\fR or \f(CW\*(C`use vars\*(C'\fR,
localized via \f(CW\*(C`my()\*(C'\fR, or wasn't fully qualified. Because this is to avoid
variable suicide problems and subtle dynamic scoping issues, a merely
\&\fIlocal()\fR variable isn't good enough. See \*(L"my\*(R" in perlfunc and
\&\*(L"local\*(R" in perlfunc.
\& $X::foo = 1; # ok, fully qualified
\& my $foo = 10; # ok, my() var
\& local $foo = 9; # blows up
\& our $bar; # Declares $bar in current package
\& $bar = 'HgS'; # ok, global declared via pragma
The \fIlocal()\fR generated a compile-time error because you just touched a global
name without fully qualifying it.
Because of their special use by \fIsort()\fR, the variables \f(CW$a\fR and \f(CW$b\fR are
exempted from this check.
.ie n .IP """strict subs""" 6
.el .IP "\f(CWstrict subs\fR" 6
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 \f(CW\*(C`=>\*(C'\fR symbol.
\& $SIG{PIPE} = Plumber; # blows up
\& $SIG{PIPE} = "Plumber"; # just fine: quoted string is always ok
\& $SIG{PIPE} = \e&Plumber; # preferred form
See \*(L"Pragmatic Modules\*(R" in perlmodlib.
\&\f(CW\*(C`strict 'subs'\*(C'\fR, with Perl 5.6.1, erroneously permitted to use an unquoted
compound identifier (e.g. \f(CW\*(C`Foo::Bar\*(C'\fR) as a hash key (before \f(CW\*(C`=>\*(C'\fR 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) '...'
projects / OpenSPARC-T2-SAM / blob