This is EXACTLY what I was looking for, thank you so much!!

Because I'm 99% sure I know the last few characters, my bruteforcer now looks like this:

#!/usr/bin/perl

use Digest::SHA 'sha256';
use MIME::Base64;

use Data::Dumper;
$Data::Dumper::Useqq = 1;

#my $target = "KGOnPYya2qwhF9w4xK157EZZ/RqIxParohltZWU7h2T/VGjNRA=="; 
+# VMware1234!
my $target = "(my actual hash goes here)"; # Unknown
my ($hash, $salt) = unpack("a32 a*", decode_base64($target));


my $chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTU
+VWXYZ.,-_|!#%=+?'*";
my $base = length($chars);
my $guess = "";
my $known = "(the known part of the password goes here)";
my $count = -1;

while (1) {
  
  my $digest = sha256($salt . $guess . $known);
  if ($digest eq $hash) {
    print "Password: '$guess$known'\n";
    exit;
  }

  $count++;
  my $temp = $count;
  $guess = "";
  while ($temp) {
    $guess = substr($chars, ($temp % $base), 1) . $guess;
    $temp = int($temp / $base);
  }
  
  print "Searching for $target: ($count) '$guess$known'\n" unless $cou
+nt % 1000000;
}
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