I would like to write a function which takes a a Perl block (not anonymous sub) and evaluates it in a context in which it can access a lexically scoped variable called file. Here is my attempt: 
sub x {
    my $coderef = shift;

    use Data::Dumper; Data::Dumper->Dump([$coderef],['coderef']);

    {
    my $file = 'hoho.txt';

    $coderef->();
    }
}

$sub = sub { print "$file.YYY" }

x $sub;

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I am told "not a CODE reference at line 9" (the line where I attempt to dereference what I had hoped would be a code reference.

In reply to passing and processing code references by Anonymous Monk

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