Is there a Perl shortcut to count the number of matches in a string?

Question

Suppose I have:

my $string = \"one.two.three.four\";

How should I play with context to get the number of times the pattern found a match (3

Answer 1

I think the clearest way to describe this would be to avoid the instant-cast to scalar. First assign to an array, and then use that array in scalar context. That's basically what the = () = idiom will do, but without the (rarely used) idiom:

my $string = "one.two.three.four";
my @count = $string =~ /\./g;
print scalar @count;

Answer 2

my $count = 0;
my $pos = -1;
while (($pos = index($string, $match, $pos+1)) > -1) {
  $count++;
}

checked with Benchmark, it's pretty fast

Answer 3

Friedo's method is: $a = () = $b =~ $c.

But it's possible to simplify this even further to just ($a) = $b =~ $c, like so :

my ($matchcount) = $text =~ s/$findregex/ /gi;

You could thank just wrap this up in a function, getMatchCount(), and not worry about it destroying the passed string.

On the other hand, you can add in a swap, which may be a bit more computation, but does not result in altering the string.

my ($matchcount) = $text =~ s/($findregex)/$1/gi;