I’m not familiar with Parse::RecDescent, but by reference to the docs plus a bit of trial-and-error I got this to work by adjusting the regex and assigning $1 to a local variable (see the section “Start-up Actions” in Parse::RecDescent):

#! perl
use strict;
use warnings;
use 5.012;

use Data::Dumper;
use Parse::RecDescent;

$::RD_ERRORS = 1;   # Parser dies when it encounters an error
$::RD_WARN   = 1;   # Enable warnings- warn on unused rules &c.
$::RD_HINT   = 1;   # Give out hints to help fix problems.
#$::RD_TRACE  = 1;   # if defined, also trace parsers' behaviour

our %HASH;

my $grammar = <<'END_OF_GRAMMAR';

    {
        my $directory;
    }

    startrule: from_clause 

    from_clause: 'from' dir(s)
    {
        print "-->$directory<--\n";
        $main::HASH{dir} = $directory;
    }

    dir: m{ ^ ( .*? / .* ) $ }x
    {
        $directory = $1;
    }

END_OF_GRAMMAR

my $parser = Parse::RecDescent->new($grammar) or die   "Bad grammar!\n
+";
defined $parser->startrule("from ./foo")      or print "Bad text!\n";

say Dumper(\%HASH);
[download]

Output:

18:38 >perl 505_SoPW.pl
-->./foo<--
$VAR1 = {
          'dir' => './foo'
        };


18:51 >
[download]

Note that setting $::RD_TRACE = 1; is useful for understanding what the parser is doing.

Hope that helps,