These special cases are fairly easy to accommodate:

  1. To prevent 4 consecutive digits from being wrongly identified as a year, specify that the digits occur at the start of the right-hand string:

    if (my @m = $right =~ /^\d{2}(\d{2})(.*)/)
#                      ^ Add this

    [download]

    Within a regex, the special character ^ means “match at the start of the line.”

  2. To remove spaces, use the substitution operator (with the /g modifier for global replacement):

    $right =~ s/\s+//g;

    [download]

  3. As for 2.

  4. To prevent the string from ending in a dash, use the substitution operator again:

    $right =~ s/-$//;

    [download]

    $ is another special regex character: it means “match at the end of the line.”

See “Metacharacters” in perlre.

Note the value of using a test-driven approach: I was able to add the 4 new input/output pairs to %data, make changes to get the new test cases to pass, and know that these modifications did not invalidate the original solution (because the 4 original test cases still pass).

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^3: reg expression question by Athanasius
in thread reg expression question by healingtao

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