Take off the 'g' modifier. Otherwise, your code is fine:

# open my $fh, '/home/test.xml' or die $!;
my $fh = \*DATA;

while (<$fh>) {
    next if m{<INFO>(.*?)</INFO>}i;
    print;
}

__DATA__
  <COMPLETE>
    <T>test</T>
    <L>light</L>
    <INFO>information</INFO>
  </COMPLETE>

   <COMPLETE>
     <T>test</T>
     <L>light</L>
     <INFO>informa</INFO>
  </COMPLETE>
[download]

Would be better if your used an xml parser like XML::Twig though.