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

my $x = "xyzzyblahxyzzymoreBLahxyzzyasdfouyXYZZY";

print "Input = $x\n";
my $count = $x =~ s/xyzzy//gi;
print "count = $count\n";
print "result = $x\n\n";

$x = "blahxyzzy";
print "Input = $x\n";
$count = $x =~ s/xyZzy//gi;
print "count = $count\n";
print "result = $x\n";

__END__
PRINTS:
Input = xyzzyblahxyzzymoreBLahxyzzyasdfouyXYZZY
count = 4
result = blahmoreBLahasdfouy

Input = blahxyzzy
count = 1
result = blah