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

print str_count('AAAA', 'AA'), "\n";

sub str_count {
    my ($str, $pat) = @_;
    my $tot;
    for ( 0 .. length( $str ) - length( $pat ) ) {
        $tot++ if index($str, $pat, $_) - $_ == 0;;
    }
    return $tot;
}