Are you actually using utf8 in your source code? If so, you must have it. If not, you don't.

I don't see why you'd want to include something that doesn't help. If some future maintainer finds they want to use utf8, they can easily add use utf8 to the top.

Hi,

thank you for your comment. After your answer I've seen that the context of my question was not precise enough.

Take the following example:

die ("Was für ein Müll!");
[download]

This is a German string saying "What a rubbish!". There are umlauts in that string. When I store this source code file Latin-1 encoded there is one byte per German umlaut. The string is interpreted as a byte string. And this byte string gets interpreted correctly as Perl assumes Latin-1 encoding. But: When you run in an UTF-8 environment you would see a square and not an 'ü' when the program dies. When you use ONLY Ascii characters it doesn't matter and you're never aware of this subtle difference.

So with use utf8; and a correct source code file encoding I would force a character semantic of this string which would result in a subtle different semantic of the string thrown.

And I want to know whether there are pitfalls, when someone is using a module with that pragma probably expecting the good old byte string world.

Best regards
McA

And I want to know whether there are pitfalls, when someone is using a module with that pragma probably expecting the good old byte string world.

What would you expect to happen in that case? (I can't imagine things working correctly except by accident.)

Incidentally if your original question is not precise enough you can edit it or add more information. Its traditional to highlight the fact that you've put more information in by adding the word Update to show what you've added.

A Monk aims to give answers to those who have none, and to learn from those who know more.

There are umlauts in that string. When I store this source code file Latin-1 encoded there is one byte per German umlaut. The string is interpreted as a byte string. And this byte string gets interpreted correctly as Perl assumes Latin-1 encoding.

I don't thinks it's entirely accurate to say "Perl assumes Latin-1". It's probably better to say that Perl assumes binary or byte semantics - the bytes from your source code will be output unmodified. If the characters in the source code were in ISO8859-5 Cyrillic it would also "work" in the way you describe.

However, I would recommend that if you have non-ASCII characters in your source code, you should save the source file in UTF8 format and add the use utf8; pragma.

It's not a style issue. use utf8; tells Perl the file is encoded using UTF-8. If the file is encoded using UTF-8, use use utf8;. If your source code is encoded using US-ASCII or iso-8859-1, don't use use utf8;. It's that simple.

(Whether you encode your file using UTF-8 or not would be a style issue, but I don't see any real difference.)