G'day NewLondonPerl1,

This looks like a simple assignment to me:

#!/usr/bin/env perl

use 5.010;
use strict;
use warnings;

use Getopt::Long;

my %opts;

GetOptions(\%opts, qw{conf|c=s});

my $master_conf = $opts{conf};

say $master_conf;
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Here it is in action:

$ pm_getopt_var.pl --conf conf_value
conf_value
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Depending on where you do the assignment, you may want:

$master_conf = $opts->{conf};
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The only place in your posted code that you mention $master_conf is in what appears to be a standalone piece of code with no obvious connection to other parts of your script:

my $json_data = extract_json("$master_conf");
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Where were you intending to declare this variable? Where were you intending to assign it a value? I suspect one problem you have here is that you can't see the wood for the trees: probably 80% of the code you've posted has nothing to do with the issue at hand. Try making a simple, cut-down version of the script; when that's working, add in more complexity.

From the code you've posted, my best guess as to what you want is something like this:

# shebang and use <whatever> lines here

my $opts = getoptions();

my $master_conf = $opts->{conf};

# do something with $master_conf here (validation perhaps)

my $json_data = extract_json($master_conf);
my $decoded_json_obj = decode_json($json_data);

# do something with $decoded_json_obj here

# subroutine definitions here
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