#!/usr/bin/perl

use strict;

while(<DATA>) {
    my ($line) = $_ =~ /\b(start\s.*end)\b/;
    print "$line\n" if ( $line );
}

__DATA__
asdasd start asdasd asdasdasd asdasdas end asdasdas

adasdas start as asdas dasdasdad asdasddas end qweqwe

asdasd start asdsadsdasddasds sdasdas asdasdasdasd asdasdsa asdasd asdasdasd end