IIRC, this also works: 

$gold if 0;

[download]

It doesn't modify the var. It doesn't result in any run-time code at all.

Demo: 

$ perl -Mv5.10 -we \
'do { my $x = 42; sub {          say eval q{$x} } }->()'
Variable "$x" is not available at (eval 1) line 1.
Use of uninitialized value in say at -e line 1.


$ perl -Mv5.10 -we \
'do { my $x = 42; sub { $x if 0; say eval q{$x} } }->()'
42

[download]

Update: Tested and added demo.

In reply to Re^3: trouble with packages/eval/variable-scoping by ikegami
in thread trouble with packages/eval/variable-scoping by Ratazong

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