Write a Perl script to find, for each input line, the longest substring that appears at least twice within the line, without overlapping. (Warning: This is harder than it sounds. Remember that by...

Write a Perl script to find, for each input line, the longest substring that appears at least twice within the line, without overlapping. (Warning: This is harder than it sounds. Remember that by default Perl searches for a leftmost longest match.) Perl provides an alternative (?:... ) form of parentheses that supports grouping in regular expressions without performing capture. Using this syntax, Example 14.57 could have been written as follows:

What purpose does this extra notation serve? Why might the code here be preferable to that of Example 14.57?