In the beginning of a Perl Romance, your skills will get better every hour you spend learning and writing perl, similar to Moore's law. So, every time you look back at your past work, you are always disappointed. The beauty and nature of Perl is so that, you will solve your problem now, and that is a beautiful thing, and you will also recognize more problems that Perl can solve and will keep coming back.

It is always best to post some compilable code here so we get an idea of the context of your question. Here are some random ways to call subroutines and I think the pitfalls become evident of bad design choice. The principles are: have very descriptive and appropriate variable names, and keep your namespace as uncluttered as possible. And, as in life, always do whatever you want. Counter example follows

#!/usr/bin/env perl
package a;
use strict;
use warnings;
use lib (',');

sub double {
  return 2*$_[0];
}


package main;
use strict;
use warnings;
use feature 'say';
use Cowbell qw(thrice);

sub double {
  return "$_[0]" . $_[0];
}

sub twice {
  return a::double($_[0]);
}


say a::double(2); #4
say double(2);  #22
say thrice(2); #6

say thrice(2) - twice(3) + double(22) + 1;
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#!/usr/bin/env perl
package Cowbell;
use strict;
use warnings;
use Exporter 'import';
our @EXPORT_OK = qw (thrice);

sub thrice {
  return 3*$_[0];
}
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$OpenFileFillWeeklyTimeArray::WeeklyTimeArrayRef
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Without seeing your code, I can't say how Perl discovered that $OFFWTA_WeeklyTimeArrayRef is the same as $OpenFileFillWeeklyTimeArray::WeeklyTimeArrayRef (or at least, as references, their references are the same). Generally, it doesn't work:

#!/usr/bin/perl
use warnings;
use strict;

{   package SomeVeryLongPackageName::ToBeBoringToType;

    our $PackageArrayRef = [];

    sub init {
        push @$PackageArrayRef, localtime, @_;
    }

}

our $SVLPNTBBTT_PackageArrayRef; # How did you tell Perl this is the s
+ame ref?

SomeVeryLongPackageName::ToBeBoringToType::init(1);
print join "\n", @$SomeVeryLongPackageName::ToBeBoringToType::PackageA
+rrayRef;
print join "\n", @$SVLPNTBBTT_PackageArrayRef;
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Further to trippledubs's reply (update: and choroba's reply):   DarrenSol: You say, in effect, "I wrote some code and then wrote another version of that code. Both versions seem to work. Please tell me which version is to be preferred and why, but I'm not going to show you either version! Many thanks in advance."

IMHO, what you need to do is provide us with two (or more!) small, self-contained, compilable and executable code examples that we can all ponder and discuss. We may then be able to provide you with advice for which you can thank us!

Um, I think you need to read all these Tutorials: Variable Scoping in Perl: the basics,
Coping with Scoping , Mini-Tutorial: Perl's Memory Management,
Lexical scoping like a fox,
Read this if you want to cut your development time in half!,
zentara package/module tutorial