# man > Config::Extensions

---
type: CommandReference
command: Config::Extensions
mode: perldoc
section: 3perl
source: perldoc
---

## Quick Reference

- `use Config::Extensions '%Extensions';` — load the module to access the `%Extensions` hash
- `$Extensions{ModuleName}` — returns `'dynamic'`, `'nonxs'`, or `'static'` if built, `undef` otherwise

## Name

Config::Extensions - hash lookup of which core extensions were built.

## Synopsis

perl
use Config::Extensions '%Extensions';
if ($Extensions{PerlIO::via}) {
    # This perl has PerlIO::via built
}
## Description

The `Config::Extensions` module provides a hash `%Extensions` containing all the core extensions that were enabled for this perl. The hash is keyed by extension name, with each entry having one of 3 possible values:

- `dynamic` — the extension is dynamically linked
- `nonxs` — the extension is pure perl, so doesn't need linking to the perl executable
- `static` — the extension is statically linked to the perl binary

All values evaluate to true, so a simple `if` test is sufficient to determine whether an extension is present.

All the data used to generate the `%Extensions` hash is already present in the `Config` module, but not in such a convenient format for quick reference.

## See Also

- [Config](https://perldoc.perl.org/Config) — Perl configuration details