It's much like SteveAZ98 did below.

See the readdir page for most of an example:

    opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";
    @dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);
    closedir DIR;
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Which we can adapt like:

    opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";
    @files = grep {/\.txt$/} readdir(DIR);
    closedir DIR;
    unlink @files;
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Notice that unlink is not related to the directory functions. Also, arturo reminded me that the filesystem is considered untrusted, so this still may not work with Taint checking.