Even if Perl did detect the constant nature of the inline hashes, which I seriously doubt it could, something like this is probably clearer

use constant {
    SUBSTITUTES =>       { # substitute these
        'DUTCH'       => 'NETHERLANDS',
        'GERMANY'     => 'DEUTSCHLAND',
        'AUST.'       => 'AUSTRALIA',
    },
    SKIPWORDS => { # skip these
        'BANK'        => 1,
        'CORP'        => 1,
        'GOVERNMENT'  => 1,
        'GOVT'        => 1,
        'LIMITED'     => 1,
        'LTD'         => 1,
        'NPV'         => 1,
        'COM'         => 1,
   },
};
    
sub words {
  return [
    map { 
        SUBSTITUTES->{$_} or $_ 
    } grep { 
        !SKIPWORDS->{$_}
    } split /\s+/, shift ];
}
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