use of require in Perl

Question

I'm trying to use require multiple times in my code, but I can to run it once.

if ($value =~ "test") {
  require "mycode1.pm";  # Execute perfect
}

if ($value =~ "code") {
    require "mycode1.pm";  # Not execute
}

if ($value =~ "last") {
  require "mycode1.pm";    # # Not execute
}

I don't understand why it doesn't run, could you please help me?

[`require`](https://perldoc.perl.org/functions/require) is used to ensure that a module has been loaded, if it has already been loaded once it will not be loaded again. If you want to run the code in a file multiple times you can use [`do`](https://perldoc.perl.org/functions/do) — Håkon Hægland, Oct 20 '21 at 20:30
Does this answer your question? [In Perl, is it better to use a module than to require a file?](https://stackoverflow.com/questions/2180554/in-perl-is-it-better-to-use-a-module-than-to-require-a-file) — zb226, Oct 20 '21 at 20:39
See [What is the difference between library files and modules?](https://stackoverflow.com/a/6379109/589924) — ikegami, Oct 20 '21 at 21:43
just make a sub and call it when needed. it's no specific for Perl only, a general practice, that's why sub's are made for. — Reflective, Oct 21 '21 at 08:42

score 1 · Answer 1 · answered Oct 21 '21 at 10:29

As you've been told in the comments, Perl keeps a record of which libraries have already been loaded, so require will only be called once for each file.

A couple of notes on your code.

The right-hand operand to the binding operator should be a match (m/.../), a substitution (s/.../.../) or a transliteration (tr/.../.../). You're using strings, which are silently converted to matches at runtime - but it's better to be more explicit.

$value =~ /test/

Given that the results of your three if tests are all the same, it's probably worth converting them into a single test.

if ($value =~ /test|code|last/) {
   ...
}

use of require in Perl

1 Answers1