"require MIME::Base64" vs. "use..."

tel2 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,

I'm using Perl 5.10.1 on Linux and if I run this code:

#!/usr/bin/perl
#...miscellaneous code here...
require MIME::Base64;
$x = encode_base64('abc');
[download]

it fails with this error: "Undefined subroutine &main::encode_base64 called at ./test.pl line 4."

Changing the "require" to "use" avoids the error.

Why do I get the above error when I "require", but not when I "use"?

(I was wanting to use "require" because this part of the code is rarely executed, so I thought this would be (slightly) more efficient.)

Thanks.
Tel2

Comment on "require MIME::Base64" vs. "use..." Download Code

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Re: "require MIME::Base64" vs "use..." by stevieb (Canon) on Jul 07, 2015 at 02:45 UTC
Try: `require MIME::Base64; import MIME::Base64; $x = encode_base64('abc');` [download] `use` implies both `require` and `import`, so see if that fixes the issue. EDIT: For those future readers, the reason why its a performance benefit in certain cases to `require` and `import` instead of `use` is because `use` is run at compile time, so no matter where you `use` a module, it's loaded permanently throughout the entire run of your process. Conversely, `require` loads a module at runtime, and once the scope it is used in ends, the module is unloaded. Therefore, for parts of your program that are rarely called that need specific modules, it's often preferable to `require` them for their short lives and reduce the memory footprint of your application. -stevieb	[reply] [d/l] [select]
Re^2: "require MIME::Base64" vs "use..." by tel2 (Pilgrim) on Jul 07, 2015 at 03:18 UTC
Yes, that works thanks stevieb! So "require" was insufficient by itself because I was trying to access one of the functions of MIME::Base64, but that function hadn't been imported, right?	[reply]
Re^3: "require MIME::Base64" vs "use..." by 1nickt (Canon) on Jul 07, 2015 at 03:33 UTC
Yes, and you could have used it anyway if you called it by its full package name: `#!/usr/bin/env perl use strict; use warnings; use 5.010; require MIME::Base64; my $x = MIME::Base64::encode_base64('abc'); say $x;` [download] `$ perl 1133493.pl $ YWJj $` [download] Note the extra new line ... you will probably want to `chomp` what you get back from `encode_base64` .... Remember: Ne dederis in spiritu molere illegitimi!	[reply] [d/l] [select]
Re^4: "require MIME::Base64" vs "use..." by tel2 (Pilgrim) on Jul 07, 2015 at 08:56 UTC
Re: "require MIME::Base64" vs "use..." by Anonymous Monk on Jul 07, 2015 at 02:43 UTC
Because of import, see use/require and zentara package/module tutorial	[reply]
Re^2: "require MIME::Base64" vs "use..." by tel2 (Pilgrim) on Jul 07, 2015 at 03:15 UTC
Thanks for that, Anonymous Monk!	[reply]