package configthing;
use strict;
use Cwd 'getcwd';
use File::Basename;
use fields qw(
  # snipped for brevity...
);

our %DEFAULTS = (
  # snipped for brevity...
);

1;

sub new {

    my $this = shift;

    unless (ref $this) {
        $this = fields::new($this);
    }

    # properties (keys in the pseudohash) we set when an
    # object is initialized
    $this->{pname} = basename($0);
    $this->{pdir}  = dirname($0);
    if ( exists($ENV{'TERM'}) && '' ne $ENV{'TERM'} ) {
        $this->{is_interactive} = 1;
    }
    else {
        $this->{is_interactive} = 0;
    }

    # define empty values for all known configuration keys
    our %FIELDS;
    foreach my $k ( keys(%FIELDS) ) {
        $this->{$k} = '' unless defined($this->{$k});
    }

    # initialize default values
    our %DEFAULTS;
    foreach my $k ( keys(%DEFAULTS) ) {
        $this->{$k} = _expand_value($this, $DEFAULTS{$k});
    }

    return $this;
}
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doh! I'm mising the bless($this, 'configthing'); which explains why I put 33 separate bless($cfg) incantations all over the place. Dusty code that I obviously didn't understand when I wrote it.