What version of Perl are you using? The original usage example

    use Filter::Handle qw/subs/;
    Filter \*STDOUT, sub { "Foo: @_\n" };
    print "Bar";
    UnFilter \*STDOUT;
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works for me correctly in 5.6.2, but fails in 5.10.1 with

Deep recursion on subroutine "Filter::Handle::PRINT" at .../lib/Filter
+/Handle.pm line 51.
Segmentation fault (core dumped)
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When I replace $_[0] with shift, it fails in all the versions from 5.6.2 to blead:

Not a GLOB reference at .../lib/Filter/Handle.pm line 50.
    (in cleanup) Not a GLOB reference at .../lib/Filter/Handle.pm line
+ 25 during global destruction.
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> it's a shame that this is no longer on CPAN

See Text::OutputFilter.