You're double encoding, you use one or the other, not both. 
#!/usr/bin/perl --

use strict;
use warnings;

my $base = 'system.sysDescr.0 : DISPLAY STRING- (ascii):  ';
my $one = quotemeta $base;
my $two = "\Q$base\E";
print "$_\n" for $base, $one, $two, "\Q$one\E", "\Q$two\E";
__END__
system.sysDescr.0 : DISPLAY STRING- (ascii):
system\.sysDescr\.0\ \:\ DISPLAY\ STRING\-\ \(ascii\)\:\ \
system\.sysDescr\.0\ \:\ DISPLAY\ STRING\-\ \(ascii\)\:\ \
system\\\.sysDescr\\\.0\\\ \\\:\\\ DISPLAY\\\ STRING\\\-\\\ \\\(ascii\
+\\)\\\:\\\ \\\
system\\\.sysDescr\\\.0\\\ \\\:\\\ DISPLAY\\\ STRING\\\-\\\ \\\(ascii\
+\\)\\\:\\\ \\\

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In reply to Re^5: No matching by Anonymous Monk
in thread No matching by o_chfa

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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