$a=1;
print "Match\n" if "aa1" =~ /^(a)\1$a$/; # not match!

##</code><code>##

print "Match\n" if "aa1" =~ /^(a)\11$/; # not match!

##</code><code>##

$a='\11';
print "Match\n" if "aa1" =~ /^(a)$a$/; # not match!