'Hello World' =~ /(hello)/i;
print $1; # prints 'Hello'

##</code><code>##

my %template = (
        tag1    => 'test1',
        tag2    => 'test2',
);

while (<DATA>) {
  print "before: $_";
  s/%([^%]+)%/$template{lc($1)}/ge;
  print "after:  $_";
}

__DATA__
%tag1% some text %TAG2% some more text