Count occurrences of a substring

The task is to either create a function, or show a built-in function, to count the number of non-overlapping occurrences of a substring inside a string. The function should take two arguments: the first argument being the string to search and the second a substring to be search for. It should return an integer count.

<lang pseudocode>print countSubstring("the three truths","th") 3

// do not count substrings that overlap with previously-counted substrings: print countSubstring("ababababab","abab") 2</lang>

Perl

This solution uses regex, hence the substring cannot contain regex metacharacters <lang perl>sub countSubstring {

 my ($str, $sub) = @_;
 my $count = () = $str =~ /$sub/g;
 return $count;

or return scalar( () = $str =~ /$sub/g );

}

print countSubstring("the three truths","th"), "\n"; print countSubstring("ababababab","abab"), "\n";</lang>

Python

<lang python>>>> "the three truths".count("th") 3 >>> "ababababab".count("abab") 2</lang>

Tcl

The regular expression engine is ideal for matching this, especially as the ***= prefix makes it interpret the rest of the argument as a literal string to match: <lang tcl>proc countSubstrings {haystack needle} {

   regexp -all ***=$needle $haystack

} puts [countSubstrings "the three truths" "th"] puts [countSubstrings "ababababab" "abab"]</lang>

Output:

3
2