I'll update my Best Practices.
perlcritic detects this by default: 
Variable declared in conditional statement at line , column .  Declare
+ variables outside of the condition.  (Severity: 5)

[download]
Perl::Critic::Policy::Variables::ProhibitConditionalDeclarations

In reply to Re^3: Closure warning with Perl 5.14? (perlcritic) by toolic
in thread Closure warning with Perl 5.14? by BerntB

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