in reply to Using a 'package' as a 'module', and choosing at runtime?

If I understand correctly, you want to have multiple modules together with the main script all in the same file. One way I can think of, without excessive rewrite, is by using a scalar reference to point to required package code at run-time, sort of a poor-man's dynamic link library.

#!/usr/bin/perl -w
my $pkg;
BEGIN {
    if    ( $^O =~ /dar/ ) { $pkg = \&mac::get_answer }
    elsif ( $^O =~ /sol/ ) { $pkg = \&sun::get_answer }
    elsif ( $^O =~ /aix/ ) { $pkg = \&aix::get_answer }
    else                   { die "unknown os." }
};

print "answer is " . &$pkg() . "\n";
exit 0;

package mac;
sub get_answer { return "Apple" }

package sun;
sub get_answer { return "Sun" }

package aix;
sub get_answer { return "IBM" }

__END__

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Re: Re: Using a 'package' as a 'module', and choosing at runtime?
by hardburn (Abbot) on Oct 28, 2003 at 16:32 UTC

    References to package subroutines are always done symbolically (even with strict 'refs' on), so you only need to change how the package is called.

    #!/usr/bin/perl -w
my $pkg;
BEGIN {
    if    ( $^O =~ /dar/ ) { $pkg = 'mac' }
    elsif ( $^O =~ /sol/ ) { $pkg = 'sun' }
    elsif ( $^O =~ /aix/ ) { $pkg = 'aix' }
    else                   { die "unknown os." }
};

print "answer is " . $pkg->get_answer() . "\n";
exit 0;

package mac;
sub get_answer { return "Apple" }

package sun;
sub get_answer { return "Sun" }

package aix;
sub get_answer { return "IBM" }

__END__

    [download]

    Which makes it a lot easier to add new class methods in the future.

    ----
    I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
    -- Schemer

    :(){ :|:&};:

    Note: All code is untested, unless otherwise stated

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      Excellent! Thanks so much; this looks exactly like what I want to accomplish.
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