#!/usr/bin/perl
use strict;
use warnings;

my $string    = "PHAGEPHAGEPQKREPHAGEPWSQEPHAGEPRDLEPHAGE";
my $substring = "PHAGE";

my $count    =  0;
my $last_pos =  -1;

NAKED:
	{
	$last_pos = index( $string, $substring, $last_pos + 1 );
	last if $last_pos == -1;
	
	print "Found $substring at $last_pos\n";
	$count++;
	redo;
	}
	
print "Found $count instances of $substring\n";

__OUTPUT__
Found PHAGE at 0
Found PHAGE at 5
Found PHAGE at 15
Found PHAGE at 25
Found PHAGE at 35
Found 5 instances of PHAGE

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

my @array    = split //, "PHAGEPHAGEPQKREPHAGEPWSQEPHAGEPRDLEPHAGE";
my @subarray = split //, "PHAGE";

my $offset   =  0;
my $count    =  0;

NAKED:
	{
	foreach my $index ( 0 .. $#subarray )
		{
		next if $array[ $offset + $index ] eq $subarray[ $index ];
		$offset += 1;
		redo NAKED;
		}
	
	print "Found @subarray at $offset\n";
	$count++;

	$offset += @subarray;
	last if $offset + @subarray > @array;
	
	redo;
	}
	
print "Found $count instances of @subarray\n";

__OUTPUT__
Found P H A G E at 0
Found P H A G E at 5
Found P H A G E at 15
Found P H A G E at 25
Found P H A G E at 35
Found 5 instances of P H A G E