Sorry; I can't answer your question because I can't understand it. Let me try to show you how I think you might ask.

I have the following input data:

block1 start hehu7 gjwsdh hsjdhj remove hjhsj 
jdkwj hwjdhjwh end block2 start crgr hjdhwjd 
wjdkwj wkjw g hjhd end
[download]

I want to remove the string that starts with 'start', includes 'remove', and ends with 'end':

block1  block2 start crgr hjdhwjd 
wjdkwj wkjw g hjhd end
[download]

Of course this may not be what you want at all. Why not try to be a bit more explicit and we'll see what we can do to help?

ya, this is what I want.......

Here is your solution:

my $str = <<'EOB';
start
    hehu7 gjwsdh hsjdhj remove hjhsj
    jdkwj hwjdhjwh
end
start
    crgr hjdhwjd
    wjdkwj wkjw g hjhd
end
EOB

while ($str =~ /(\bstart\b.*?\bend\b\s*)/gs) {
    my $block = $1;
    if ($block =~ /\bremove\b/) {
        $str =~ s/\Q$block\E//;
    }
}
print $str;

__END__
start
    crgr hjdhwjd
    wjdkwj wkjw g hjhd
end
[download]