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Adding Functionality to the Perl Baseline
- The Perl interpreter needs to load information about many
different things at startup. Therefore, it doesn't load every possible
thing, but takes cues from the programmer about what is needed.
- The use of Perl's use and require are similar
to Java's import or C/C++'s include statements.
- use loads in modules at compile time, while
require waits until run time. Thus, use is
usually prefered.
- The @INC array specifies the search path to employ
when looking for add-in modules. This will include your
current directory.
Quick use vs. require example
use.pl:
#!/usr/bin/perl -w
# This loads in a module called "strict":
#use strict;
# This loads in a module called "use-in"
use using;
# This loads in a file (which might not be a module) called "using.pl"
require "using.pl";
print $blah::test . ", ";
print $test . "\n";
--
using.pm:
# .pm packages are loaded at compile time, so should not include
# interactive content
package blah;
our $test="hi there";
return 1;
--
using.pl:
# Import via "require" happens at run-time, so we can include
# interactive items:
print "Welcome to using.pl\n";
our $test="big guy";
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- We'll have more about using and creating modules in
future classes.
- For now: consider putting shared functionality in a separate
file that you can re-use for many different programs. This works
very well for your own subroutines.
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