I'd like to be able to pass a subroutine a conditional test and a value to test against it. For example the conditional could be a hash ...

Just a thought in case you do go ahead and implement this yourself: Implementing a query language means grammar design + parser + interpreter + tests for everything... why not write the conditionals in Perl?

my $conditional_test = sub {
   my $value = shift;
   return $value==10022 || $value==96813 || $value==55401;
};

if( $conditional_test->($redis_handle->get('key')) ) {
   # do something
}
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Plenty of examples of this: sort, File::Find, ... MJD's Higher-Order Perl is an excellent read in this respect.