$data = q`
HTML1
<% CODE1 %>
HTML2
<% CODE2 %>
HTML3
`;

  while( $data =~ /(.*?)<%(.*?)%>\n?/gs ) {
    print "<<< $1 >>>\n" ;
    print "<<< $2 >>>\n" ;
  }

  if ( $data =~ /.*<%.*?%>\n?(.*?)$/s ) {
    print "<<< $1 >>>\n" ;
  }