#!/usr/intel/bin/perl
use warnings;
use strict;

my $find_flag;                            #using a flag variable

while ( <> ){
  if (/^\S/){                             #match a line that start with no space
    if (/^\w+clk\[\d+\]/){                #match requested headline
      $find_flag = 0;
    }
    else{
      $find_flag = 1;
    }
  }
  next if $find_flag and /\s+QUALIFIED_CLOCK/;     #skips the line requested
  print qq{$_};                                    #printing ordinary line
}