Hello monks!

I need wisdom and sage advice about the Right Way ( or Ways ) to pull in modules at runtime. This is along the lines of getting the name of the module in runtime and calling a function from that module, but in an OO context.

Consider my situation:

The goal is this -- I have many different types of data collections in different languages, including nontext data - I want to be able to select the appropriate parser from a config file so that I can benefit from polymorphism. I ask the parser for word lists, and I don't want to worry about what 'word list' means for that docment collection. For some it will mean splitting on white space, for others it will be sophisticated part-of-speech tagging - whatever.

I have a document collection object ( LSI::Collection ) whose constructor reads a config file to figure out which parser to use. This parser can come in many, many flavors, all of them subclasses of a common ancestor, which serves as the default if none is defined in the config file.

My problem is this - some of these parsers do a lot of setup in the class constructor, which makes for a long wait at startup. Also, I don't want to clutter my Collection class with a zillion 'use' or 'require' statements. Here is a solution that I've found to dynamically require modules as needed, but it my bones it feels like the wrong way to do it: 
my $parser;
my $m = $params{'parse_method'}; # from the config file

# this is a hash of parser names to modules
my %flavors  = (
     'POS' =>    'LSI::Parser::POS', 
     'Regexp' => 'LSI::Parser::POS::Regexp', 
         'JSTOR'  => 'LSI::Parser::POS::JSTOR' 
);


my $flavor = $flavors{ $m } || 'LSI::Parser'; # default
        
# This is what makes me uneasy...
eval "require $m" ;
$self->{'parser '} = ($m)->new();

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Is there a better way to do this? What is a virtuous way to add error handling here? Humble thanks in advance.

In reply to How best to require subclasses at runtime by FamousLongAgo

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