Programming Perl, 4th Edition

strict “refs”

This generates a runtime error if you try to dereference a string instead of a reference, whether intentionally or otherwise.

See Chapter 8 for more about these.

use strict "refs";

$ref = \$foo;       # Store "real" (hard) reference
print $$ref;        # Dereferencing is ok

$ref = "foo";       # Store name of global (package) variable
print $$ref;        # WRONG, runtime error under strict refs

Symbolic references are suspect for various reasons. It’s surprisingly easy for even well-meaning programmers to invoke them accidentally; strict "refs" guards against that. Unlike real references, symbolic references can refer only to package variables. They aren’t reference counted. And there’s often a better way to do what you’re doing: instead of referencing a symbol in a global symbol table, use a hash as its own mini symbol table. It’s more efficient, more readable, and less error prone.

Nevertheless, some sorts of valid manipulation really do require direct access to the package’s global symbol table of variables and function names. For example, you might want to examine the @EXPORT list or the @ISA superclass of a given package whose name you don’t know in advance. Or you might want to install a whole slew of function calls that are all aliases to the same closure. This is just what symbolic references are best at, but to use them while use strict is in effect, you must first undo the refs stricture:

# make a bunch of attribute accessors for my $methname (qw/name rank serno/) { no strict "refs"; *$methname ...