use strict;
      3 my $var1 = "a+b";
      4 my $var2 = "a+b";
      5 if ($var1 =~ /\Q$var2\E/) {
      6     print "hey it matches \n";
      7 }
      8
      9 print "hey here  \n";
     10
[download]

use strict;

my $var1 = "a+b";
my $var2 = "a\+b";
if ($var1 =~ /$var2/) {
    print "hey it matches \n";
}

print "hey here  \n";
[download]

$var2 = "a\\+b";
[download]