first(3) - Linux man page

Name

first - use the first loadable module in a list

Synopsis

use first 'YAML::Syck', 'YAML::TINY', 'YAML';

if( $first::module ) {
    print "Looks like I'll be using $first::module for this YAML..."
}
else {
    die "I have no YAML modules: $@";
}

my $yaml = $first::module->new();

use first 'CGI::Simple', 'CGI::Minimal', 'CGI';
my $cgi = $first::module ? $first::module->new() : $fallback_obj;

Description

Two main circumstances I've encountered where this is useful is:

• when you have a list of modules that have the same interface but are more desirable for one reason or another like speed, portability, or availability.

use first 'CGI::Simple', 'CGI::Minimal', 'CGI';

• when you have a list of modules that do the same task but via different methods

use first 'YAML::Syck', 'YAML::TINY', 'YAML', 'XML::Tiny', 'XML::Simple', 'Storable';

my $serializer = $first::module;

# now use functions based on $serializer / $first::module, perhaps keeping it in a hash that maps funtions to the name space for a consistent API where none existed before

Arguments

Arguments after 'use first' can be a name space string or an array reference whose first item is a name space and the rest is what would get passed to/after 'use Name::Space'

Variables

These variables are available after 'use first' and are reset upon each call of 'use first' (Similar to how $@ is reset with every eval)

$first::module

Contains the namespace that was loaded, if any. undefined otherwise if none could be loaded.

$first::failed

Is a hashref whose keys are the name space that could not be loaded and the values are the given key's error message.

Contains the last error, if any.

Todo

More tests as per first.t

Author

Daniel Muey, <http://drmuey.com/cpan_contact.pl>

Copyright And License

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.