Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval3pm

Affiliation

This Policy is part of the core Perl::Critic distribution.

Overview

The string form of "eval" is recompiled every time it is executed, whereas the block form is only compiled once. Also, the string form doesn't give compile-time warnings.

    eval "print $foo";        # not ok
    eval {print $foo};        # ok

Configuration

There is an "allow_includes" boolean option for this Policy. If set, then strings that look like they only include an optional "package" statement followed by a single "use" or "require" statement (with the possible following statement that consists of a single number) are allowed. With this option set, the following are flagged as indicated:

    eval 'use Foo';                           # ok
    eval 'require Foo';                       # ok
    eval "use $thingy;";                      # ok
    eval "require $thingy;";                  # ok
    eval 'package Pkg; use Foo';              # ok
    eval 'package Pkg; require Foo';          # ok
    eval "package $pkg; use $thingy;";        # ok
    eval "package $pkg; require $thingy;";    # ok
    eval "use $thingy; 1;";                   # ok
    eval "require $thingy; 1;";               # ok
    eval "package $pkg; use $thingy; 1;";     # ok
    eval "package $pkg; require $thingy; 1;"; # ok
    eval 'use Foo; blah;';                    # still not ok
    eval 'require Foo; 2; 1;';                # still not ok
    eval 'use $thingy;';                      # still not ok
    eval 'no Foo';                            # still not ok

If you don't understand why the number is allowed, see Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval.

This option inspired by Ricardo SIGNES' Perl::Critic::Policy::Lax::ProhibitStringyEval::ExceptForRequire.