I always that that modules were the domain of real Perl gurus, so I did a
lot of requiring in my first Perl scripts. After running into all sorts of
problems with namespace, especially for global variable names, I decided to
check out modules. Surprise, surprise, they're simple!!
Without going into all of the theory behind them (which I didn't know the
first thing about when I started using them), here is a module.
The file name of the module is MyModule.pm, and it lives in the lib
directory off your root Perl directory.
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package MyModule;
# this tells perl that it is the MyModule module
# all modules must return a value when they compile, so stick this line
somewhere in your module -- I usually put it at the end of all my
declarations and before the main code.
return 1;
# now we can start our subroutines
# this subroutine is required to make a module a module. I won't go into
exactly what it does -- suffice to say that it creates an object
# in memory that your script can have access to. Copy and past this into
your own module.
sub new()
{
my ($proto) = @_;
my $class = ref($proto) || $proto;
my $self = {};
bless ($self, $class);
return $self;
}
# the rest of your subroutines go here.
# let's put in a dummy one, just to make sure everything is working
sub GetValue()
{
my($self) = @_;
# what's this $self stuff? Don't worry about it for now. But the
first parameter of any subroutine that you want visible to
# the outside world should be $self.
return 1;
}
sub EchoInput()
{
my($self, $input) = @_;
return $input;
}
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Now, you'll want to use your new module.
Let's say we have a script called MyScript.pl. Here it is:
___________________________________________________________________________________________
#! perl
# above is the shebang line, and you'll all notice I'm on a M$ OS :)
# let's get access to our module
# this command tells perl to grab the module and stick into memory
use MyModule;
# we still can't use it though -- we have to assign it to a variable:
my $mod = MyModule->new();
# now, $mod contains all of our subroutines in the MyModule module, which
we call like this
my $value = $mod->GetValue();
# the arrow (->) means that referring to a pointer, to use C++ terminology.
Without going into great detail, the line above in plain English
# means "set the variable $value to whatever you get back from the
subroutine GetValue inside the $mod object"
print "The value is $value\n";
my $echo = $mod->EchoInput("hello world");
print "The echo is $echo\n";
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See how easy modules are?
At 06:33 23.05.2001 +1000, you wrote:
>Hello All,
>
>I am new to Perl and putting together a script that needs about 20 reasonably
>complex subroutines.
>
>To keep the code as modular and managable as possible I would prefer not to
>define all the routines in the main script.
>
>It seems like using 'require' is the way to go (since I don't have the time or
>experience to do modules at the moment).
Aaron Craig
Programming
iSoftitler.com
