A general comment -- some indentation of your code blocks would make things easier to read.
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open PRIMES, $primefile;
while(<PRIMES>) {
push (@parray, $_);
}
close PRIMES;

# could be 
open PRIMES, $primefile;
@parray = <PRIMES>;
close PRIMES;
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if($lowrange % 2 == 0) { $lowrange++; }

# could be 

$lowrange++ unless ($lowrange % 2);
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Simple conditionals can be written as Masem pointed out. As well if you the unless you can take advantage of the fact that the result from $lowrange % 2 will be enough to tell TRUE or FALSE (1 or 0) without the additional '==' test.

Also another note on prints: When you have something like

print "\nTotal amount of primes: $counter \n";
print "Your results have been saved, starting with
".$path.$beginloc.$last."\n\n";
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You can use a single print

print "\nTotal amount of primes: $counter \n",
      "Your results have been saved, starting with
".$path.$beginloc.$last."\n\n";
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Also you can use the variables inside the double quotes:

print "Your results have been saved, starting with
".$path.$beginloc.$last."\n\n";

# becomes
print "Your results have been saved, starting with ${path}${beginloc}$
+{last}\n\n";
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The curly braces are not always required but they can alleviate some possible headaches.

Just a few notes for ya.