#index function to search substring
$a = "Ashes, ashes, we all fall down";
print index($a, "she");		#1
print "\n";
print index($a, "ashes");	#7
print "\n";
print index($a, "they");	#-1
print "\n";

@a = qw (oats peas beans);
print index (join(" ", @a), "peas"); #5, not useful
print "\n";

#indicate start searching position
$a = "Ashes, ashes, we all fall down";
print index($a, "she",5);		#8, start search at 5
print "\n";
print "============================\n";

#find all occurrences
$source = "One fish, two fish, red fish, blue fish.";
$start = -1;
while (($start = index ($source, "fish", $start)) != -1) {
	print "Found a fish at $start\n";
	$start++;
}
print "============================\n";

#search backward with rindex
$source = "One fish, two fish, red fish, blue fish.";
$start = length($source);
while (($start = rindex ($source, "fish", $start)) != -1) {
	print "Found a fish at $start\n";
	$start--;
}

print "============================\n";

#substr (string, offset, length)
#extract substring, start at position offset, length chars
$a = "I do not like green eggs and ham.";
print "length = ", length($a), "\n";
print substr($a, 0, 4);  #start at position 0, 4 chars
print "\n";
print substr($a, 14, 5);  #start at position 14, 5 chars
print "\n";
print substr($a, 5, -10);  
#start at position 5, (33-5-10)+1=18 chars
print "\n";

print "============================\n";
#use substr to replace
$a = "countrymen, lend me your wallets";
substr($a, 0, 1) = "Romans, C"; #replace first char with...
print "$a\n";
substr($a, -7, 7) = "ears."; #replace the last 7 chars
print "$a\n";