$pattern = shift;

$file = shift;
open(MAT, "<$file") or die "bad file name";


$text = <MAT>;
while($text =~ /\Q$pattern\E/g) {
 $x += 1; 
}
print "found $x matches\n";

close(MAT);
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The \Q and \E are regex "quotes". That means characters with special meaning lose those meanings and become literal. If you want the user to be able to use regex special characters, just remove the \Q & \E.