#!/usr/bin/perl

use strict;
use warnings;

my $text = '1 + 3 = [532] {hallo}';

my $string = q~+?.*^$()[]{}|\\~;
$text =~ s/([\Q$string\E])/\\$1/g;
print $text;

~/entwicklung 73> perl regexp.pl 
1 \+ 3 = \[532\] \{hallo\}