my $dir = "/Path/to/a/data/directory";
my %hash;
$hash{$_} = hashify_file( $_ ) for ls_dir( $dir );

sub ls_dir {
    my $dir = shift;

    opendir my $dh, $dir
        or die "Can't opendir '$dir': $!\n";

    return map  { "$dir/$_" }
           grep { !/^\./ && !/\~$/ } readdir $dh;
}

sub hashify_file {
    my $file = shift;

    open my $fh, '<', $file
        or die "Can't read '$file': $!\n";

    my $out;
    %{$out} = ( %{$out}, %{hashify_line( $_ )} ) for <$fh>;

    close $fh or die "Can't close '$file': $!\n";

    return $out;
}

sub hashify_line {
    my $line = shift;

    chomp $line;
    $line =~ s/^\s+//;
    return {} if ( $line =~ /^\#/ || $line =~ /^\s*$/ );
    my ( $key, @values ) = split /\t/, $line;

    return { $key => \@values };
}

##</code><code>##

my $dir = "/Path/to/a/data/directory";
my %hash;

open my $grep_fh, '-|', "grep '^' $dir/* /dev/null"
    or die "Can't grep: $!\n";
while ( my $line = <$grep_fh> ) {
    $line =~ s/^([^:])://;
    my $file = $1;
    next if $file =~ /\~$/;
    %{$hash{$file}} = (%{$hash{$file}}, %{hashify_line( $line )});
}
close $grep_fh or die "Error closing grep pipe: $!\n";

##</code><code>##

my $cmd = "find $dir -type f -print | xargs grep '^' /dev/null";
open my $grep_fh, '-|', $cmd
    or die "Can't grep: $!\n";