A="foo"
B="some other data"
C="appending $A"
D="
  some list
  with more data
  and $B
"

##</code><code>##

#!/bin/bash -

. foo.conf
export A
export B
export C
export D
./foo.pl

##</code><code>##

#!/usr/bin/perl

my %exp_vars = (
  A =>  'SCALAR',
  B =>  'SCALAR',
  C =>  'SCALAR',
  D =>  'ARRAY',
);

my $env;
foreach my $var (keys %exp_vars)
{
  my $type = $exp_vars{$var};
  my $val = lc $var;
  if (! defined $ENV{$var} or length($ENV{$var}) <= 1)
  {
    push @out, "# [$var] not exported";
    next;
  }

  if ($type eq 'ARRAY')
  {
    @{$env->{$val}} = ($ENV{$var} =~ m/(?:\s+)?(\S+)/g);
  }
  elsif ($type eq 'SCALAR')
  {
    $env->{$val} = $ENV{$var};
  }
}

##</code><code>##

#!/bin/env perl

use strict;
use warnings;

use Data::Dumper;

sub parse_sh
{
  my ($data) = @_;

  my $r;
  $data =~ s/((?: *#.*?)?\n+)/\n/gs;  # Remove comment lines
  $data =~ s/(\n+)/\n/gs;             # Remove blank lines
  $data =~ s/ *(\S+)=("?)(.*?)\2 *\n/$r->{lc($1)}="$3"/gse;

  return $r;
}

sub parse_sh_maint
{
  my ($r, $noset) = @_;

  # Interpolate variable names
  my $max_passes = 5;
  my $not_substituted;
  for (1 .. $max_passes ) 
  {
    for my $k (keys %$r)
    {
      next unless (ref(\$r->{$k}) eq 'SCALAR');
      $r->{$k} =~ s|\$(\w+)| $r->{lc($1)} // do{ "\$$1" } |ge;
      $not_substituted += $r->{$k} =~ tr/$/$/;
    }
    last unless $not_substituted;
  }

  # Remove remaining variables and make variables with spaces and newlines arrays
  for my $k (keys %$r)
  {
    $r->{$k} =~ s/\$\S+ *?//gs;               # Remove remaining variables
    $r->{$k} =~ s/\s+/\n/gs;                  # Remove leading spaces
    if (not grep { $_ eq $k } @$noset)
    {
      my %dedupe = 
        map { $_ => 1 } 
        split(/ |\n/, $r->{$k});
      $r->{$k} = ();
      @{$r->{$k}} = keys %dedupe;
    }
  }

  return $r;
}

open(my $fh, "<", $ARGV[0]);
my $content = do { local $/ = <$fh> };
my $stuff = parse_sh_maint(parse_sh($content), [qw/scalar1 scalar2/]);
print "Vars: " . Dumper($stuff), "\n";