# phpman > man > Config::Extensions

## NAME
    [Config::Extensions](https://www.chedong.com/phpMan.php/perldoc/Config%3A%3AExtensions/markdown) - hash lookup of which core extensions were built.

## SYNOPSIS
        use [Config::Extensions](https://www.chedong.com/phpMan.php/perldoc/Config%3A%3AExtensions/markdown) '%Extensions';
        if ($Extensions{[PerlIO::via](https://www.chedong.com/phpMan.php/perldoc/PerlIO%3A%3Avia/markdown)}) {
            # This perl has [PerlIO::via](https://www.chedong.com/phpMan.php/perldoc/PerlIO%3A%3Avia/markdown) built
        }

## DESCRIPTION
    The [Config::Extensions](https://www.chedong.com/phpMan.php/perldoc/Config%3A%3AExtensions/markdown) 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

    As all values evaluate to true, a simple "if" test is good enough to determine whether an
    extension is present.

    All the data uses to generate the %Extensions hash is already present in the "Config" module,
    but not in such a convenient format to quickly reference.

## AUTHOR
    Nicholas Clark <<nick@ccl4.org>>