Usage of qw(:const) with use statement

Question

Sorry for a very basic question, but I'm beginner level at Perl and could not find a suitable explanation on SO (or anywhere else!) for this question. I understand I can write a few examples and try to decipher this but I can really use some knowledge from the experts. I'm going through some code where the developer has sourced libraries using: ``` use libExample qw(:const) ``` Now from what I understand this means sourcing the constants from libExample but would really like to know how this works. Why can't I simply say: `use libExample qw(const)` (Trying to understand relevance of `:`) Is there something we can/should write in `libExample.pm` itself to make other developers utilizing this library to mention such options in place of const that is. Thanks!

Accepted Answer

```
use libExample qw(:const)
```

will pick all names in `$EXPORT_TAGS{const}` anonymous array and will import them to current namespace.

Whereas

```
use libExample qw(const)
```

will pick const and will import it in current namespace.

There are also other variants:

```
[!]name         This name only
[!]:DEFAULT     All names in @EXPORT
[!]:tag         All names in $EXPORT_TAGS{tag} anonymous array
[!]/pattern/    All names in @EXPORT and @EXPORT_OK which match
```

Please go through Exporter documentation for more details on the topic.

Usage of qw(:const) with use statement

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