That is not what the original code snippet does (it does in fact count the string length .. hence the variable named $string_length). If you pasted the code into your editor you could see if there was a space in the regex or not (not). Your code to count words, however, not only isn't -w compliant (implicit split to @_), it can very easily give wrong results:

$ths = ' this is a   string';
$i = split(/\s/,$ths);
print "$i\n";
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If you want to split a string on whitespace, use the special case of split(" ", $ths) which splits on multiple whitespace and ignores any leading null field (see: perlfunc:split for details).

$_ = ' this is a   string';
my @words = split " ";
print scalar @words, "\n";

# or you could go for this version :-)

$_ = ' this is a   string';
my $words =()= /(\S+)/g;
print $words, "\n";
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