$ cat krunk.pl
#!/usr/bin/perl
#
# Demo for flip-flop operator
#
use 5.14.0;
use warnings;
use autodie;

while (<DATA>) {
    if (/start/ .. /stop/) {
        # in combat!
        print "COMBAT: $_";
    }
}
__DATA__
soon the combat will begin
start combat!
Biff!  Pow!  Bam!
(Looks like Batman!)
stop combat
fight had three superlatives

$ perl krunk.pl
COMBAT: start combat!
COMBAT: Biff!  Pow!  Bam!
COMBAT: (Looks like Batman!)
COMBAT: stop combat