Cancel/no-op a require

sedusedan has asked for the wisdom of the Perl Monks concerning the following question:

I'm just wondering, is there a way for an import hook to cancel/ignore/no-op a require() so that this code works?

unshift @INC, \&import_hook;
require Foo; # nothing is loaded
require Bar; # nothing is loaded
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I've tried:

unshift @INC, sub {
    return (undef, sub {0});
}
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use Tie::Handle::Scalar;
unshift @INC, sub {
    tie *FH, "Tie::Handle::Scalar", ""; # or "1;\n"
    #$INC{$name} = undef; # or $name. testing
    return (*FH);
}
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Perl seems to go to the next @INC entry for all the above two cases. What am I doing wrong?

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