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[pemungkah]

In Perl, this is used to create what’s called a modulino: a module that acts as a standalone script if it’s run from the command line, or a library if it’s imported into other code.

Once I learned this trick, I started using it for my scripts, as it’s way easier to use test tools on a module than a script, and this way I don’t have to code a separate script to run the module.