open TEST,"@ARGV[0]";

##</code><code>##

open(my $TEST, "<", $ARGV[0])
   or die("Can't open \"$ARGV[0]\": $!\n");

##</code><code>##

$flag = "ON"
...
$flag = "OFF"

##</code><code>##

my $looking = 1;
...
$looking = 0;

##</code><code>##

while (<TEST>)

##</code><code>##

while (<>)

##</code><code>##

if (/test/ and $flag eq "ON")

##</code><code>##

if ($looking && /test/)

##</code><code>##

print "start";

##</code><code>##

print "start\n";

##</code><code>##

say "start";

##</code><code>##

close TEST;

##</code><code>##

use strict;
use warnings qw( all );

my $looking = 1;
while (<>) {
   if ($looking && /test/) {
      print "start\n";
      $looking = 0;
   }
}

##</code><code>##

use strict;
use warnings qw( all );

while (<>) {
   if (/test/) {
      print "start\n";
      last;
   }
}