use warnings;
use strict;


my $START = qr{ \A Info  [ ] I  [ ] Want                 }xms;
my $STOP  = qr{ \A Start [ ] of [ ] Info [ ] I [ ] don't }xms;


while (<DATA>) {

    if (/$START/ .. /$STOP/ xor /$STOP/) {
        print;
        }

    }

__DATA__
asdfsdfds
asdfasdf
blah blah blah

Info I Want

I want this line
And this line
And this line

this is the last line i want
Start of Info I don't want

blah blah
blah blah blah