#!/usr/bin/perl -w
use strict;

while (my $line = <DATA>)
{
   if ( my $include_file = 
        ($line =~ /#include\s+[<"](.*?)[>"]/)[0] 
      )
   {
      print "$include_file\n";
   } 
}

#prints:
#string.h
#stdlib.h
#sys/dispatch.h


__DATA__
INPUT:- #include "string.h" --> below code prints header
this is just a BS, nonsense line
 #include        <stdlib.h> --> below code prints header
 #include <sys/dispatch.h> --> not able to get the header name(dispatch.h)