You can put a code reference into @INC, which will be called by require when attempting to load a module. If the code reference returns undef, then require will continue on using the rest of @INC...

unshift( @INC, sub {
    my ( $self, $path ) = @_;
    $path =~ s#/#::#g;
    $path =~ s/\.pm$//;
    print "INC: $path\n";
    return undef;
} );
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