This seems to be a bug in the weird, custom import subroutine of IO::Prompter because it works when used in the traditional fashion:

perl -e'use IO::Prompter; prompt -menu => [6..9]'
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The custom import subroutine takes the second argument given to it as fake input:

# Export the prompt() sub...
sub import {
    my (undef, $config_data, @other_args) = @_;

    # ...
    if( 0 ) { # other options that do not apply
    
    # Handler faked input specifications...
    elsif (defined $config_data) {
        $fake_input = $config_data;
    }
}
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I don't understand why @_ is not as expected for it, but the code path triggered is the one for fake input data as in:

perl -e'use IO::Prompter 'fake'; prompt( -menu => [6..9] )'
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... which provides the fake input fake.

Right after posting I understand. The custom export subroutine does not take the name of the subroutine to export! Just leaving out the prompt makes things work:

perl -MIO::Prompter -e'prompt -menu => [6..9]'
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Not just you. Reproduced with the stock OS X install of 5.18.2 and IO::Prompter 0.004015.

Update: Also seeing with 5.26.2 on RHEL6 and IO::Prompter 0.004014.