The 'strict' pragma has three points of function:
1. variable declaration (compile-time)
2. bareword catching (compile-time)
3. symbolic reference catching (run-time)
The first of these is most often the bane of programmers new to 'strict'.
Saying
use strict 'vars';
means that, to the end of this scope (block or file), or until a
no strict 'vars';
is encountered, any variable used must have been declared, or must have an
explicit package name. Variables can be declared in a few ways:
1. my $foo; # a lexical (non-package related) variable
2. our $foo; # like my() for package variables
3. use vars '$foo'; # says $foo is valid in this package
You can give a variable an explicit package name, too:
1. $main::foo; # $foo in package main::
2. $::foo; # same thing
3. $Bar::foo; # $foo in package Bar::
The bareword-catching is handled by
use strict 'subs';
and has the same scope as 'vars'. It requires that all barewords be
known filehandles, declared functions, preceded by a -, inside braces,
followed by a =>, or preceded by a << (as in a here-doc).
1. open FOO, "< file";
2. sub foo { scalar reverse $_[0] } $x = foo "hi there";
3. $opt = -ok_action;
4. print $people{japhy};
5. %people = ( japhy => "Marillion" );
6. print <<END;
Any other use of a bareword (which is an bare identifier[1]) is illegal
under strict 'subs'.
The symbolic reference catching is run-time, and is enabled via
use strict 'vars';
and has the same scoping laws as the others. It stops you from doing
$name = 'japhy';
$var = 'name';
print $$var; # $$var => $name => japhy
You must use hard references:
$name = 'japhy';
$var = \$name;
print $$var;
If you just say
use strict;
all three options are enabled. You can turn on multiple options in one
"use" statement. To turn them off, use "no" instead of "use".
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
I am Marillion, the wielder of Ringril, known as Hesinaur, the Winter-Sun.
Are you a Monk? http://www.perlmonks.com/ http://forums.perlguru.com/
Perl Programmer at RiskMetrics Group, Inc. http://www.riskmetrics.com/
Acacia Fraternity, Rensselaer Chapter. Brother #734
** Manning Publications, Co, is publishing my Perl Regex book **
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