Thanks boftx!

I am still confused and must go away and do some more reading on Moose because I have taken your suggestion, but still do not get the results I am after. Below is complete code and here the new errors and output:

Use of uninitialized value in concatenation (.) or string at cos_vectors.pm line 83.
Use of uninitialized value in concatenation (.) or string at cos_vectors.pm line 83.
Use of uninitialized value in concatenation (.) or string at cos_vectors.pm line 91.
Use of uninitialized value in concatenation (.) or string at cos_vectors.pm line 87.
Use of uninitialized value in concatenation (.) or string at cos_vectors.pm line 95.
/Codar/SeaSonde/apps/combinetools/combineprocessing/CheckForCombine 0 bonc 1 "" /processings/processing_

What's particularly annoying here is that it appears that one cannot build an attribute that is 'doubly' dependent -- i.e. look at

and notice that it depends on Ddata which in turn depends on Dbase. What's also frustrating that Dsite is not concatenating in

, which is not dependent on another attribute.
Anyhow, thoroughly confused how to get this to work with Moose.

package cos_vectors;

use Moose;

######################################################################
+#########
# Package Attributes
has 'class_ver' => ( is      => 'rw',
                     isa     => 'Str',
                     default => '10.5.1'
                   );

######################################################################
+#########
# Required Attributes
has 'site' => ( is       => 'rw',
                isa      => 'Str',
                required => 1
              );

######################################################################
+#########
# Directory Attributes
has 'Dbase'     => ( is        => 'rw',
                     isa       => 'Str',
                     default   => '/Codar/SeaSonde',
                     predicate => 'has_Dbase'
                   );
has 'Dbin'      => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Dbin',
                     predicate => 'has_Dbin'
                   );
has 'Detc'      => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Detc',
                     predicate => 'has_Detc'
                   );
has 'Ddata'     => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Ddata',
                     predicate => 'has_Ddata'
                   );
has 'Dproc'     => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Dproc',
                     predicate => 'has_Dproc'
                   );
has 'Ddiag'     => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Ddiag',
                     predicate => 'has_Ddiag'
                   );
has 'Drad'      => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Drad',
                     predicate => 'has_Drad'
                   );
has 'Fopt'      => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Fopt',
                     predicate => 'has_Fopt'
                   );
has 'Fverbose'  => ( is        => 'rw',
                     isa       => 'Str',
                     builder   => '_build_Fverbose',
                     predicate => 'has_Fverbose'
                   );

######################################################################
+#########
# Directory Builders
sub _build_Dbin {
    my $self = shift;
    return $self->{Dbase}.'/apps/combinetools/combineprocessing';
}
sub _build_Detc {
    my $self = shift;
    return $self->{Dbase}.'/configs/combineconfigs';
}
sub _build_Ddata {
    my $self = shift;
    return $self->{Dbase}.'/data';
}
sub _build_Dproc {
    my $self = shift;
    return $self->{Ddata}.'/processings/processing_'.$self->{site};
}
sub _build_Ddiag {
    my $self = shift;
    return $self->{Ddata}.'/diagnostics';
}
sub _build_Drad {
    my $self = shift;
    return $self->{Ddata}.'/radialsites';
}
sub _build_Fopt {
    my $self = shift;
    return $self->{Dbin}.'/combinesite.opt';
}
sub _build_Fverbose {
    my $self = shift;
    return $self->{Dbin}.'/combineverbocity.txt';
}

######################################################################
+#########
# Diagnostic Attributes
has 'diagCCS' => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagCCS',
                   predicate => 'has_diagCCS'
                 );
has 'diagCFR' => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagCFR',
                   predicate => 'has_diagCFR'
                 );
has 'diagCCG' => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagCCG',
                   predicate => 'has_diagCCG'
                 );
has 'diagRTC' => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagRTC',
                   predicate => 'has_diagRTC'
                 );
has 'diagTA'  => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagTA',
                   predicate => 'has_diagTA'
                 );
has 'diagTD'  => ( is        => 'rw',
                   isa       => 'Str',
                   lazy      => 1,
                   builder   => '_build_diagTD',
                   predicate => 'has_diagTD'
                 );

######################################################################
+#########
# Diagnostic Builders
sub _build_diagCCS {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 1 1 0 1`;
}
sub _build_diagCFR {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 2 1 7 1`;
}
sub _build_diagCCG {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 3 1 2 1`;
}
sub _build_diagRTC {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 4 1 2 1`;
}
sub _build_diagTA {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 5 1 2 1`;
}
sub _build_diagTD {
    my $self = shift;
    return `$self->{Dbin}/GetParameter $self->{Fverbose} 6 1 1 1`;
}

######################################################################
+#########
# Methods
sub clean_Dproc {

    my $self = shift;
    unlink $self->{Dproc}.'LLUVToCombine.list';
    unlink $self->{Dproc}.'MergeTotalsInfo.ctf';
    unlink $self->{Dproc}.'XYUVToCombine.list';
    unlink $self->{Dproc}.'TotalProcessed.txt';
    unlink $self->{Dproc}.'TotalTime.txt';
    unlink $self->{Dproc}.'TotalOutput.txt';
    unlink $self->{Dproc}.'Tot_XXXX_00_00_00_0000.tv';
    unlink $self->{Dproc}.'TotxXXXX_00_00_00_0000.tv';

}

1;
[download]

script

#!/usr/bin/perl

use strict;
use cos_vectors;

my $keepgoing = 1;
#infinite loop
while ($keepgoing eq 1) {

    my $vec = cos_vectors->new( site => 'bonc' );

    print $vec->site." ".$vec->Fverbose."\n";
    $vec->clean_Dproc;
    my $syscall = sprintf("%s/CheckForCombine 0 %s 1 \"\" %s",$vec->Db
+in,$vec->site,$vec->Dproc);
    print $syscall."\n";
    #system("$vec->{Dbin}/CheckForCombine 0 $vec->{site} 1 '' $vec->{D
+proc}");

    $keepgoing = 0;

}
[download]