Perl regex causing compilation error

Question

Very new to Perl and have a problem with date validation

I have the following sub running to check that user date input conforms to YYYY-MM-DD

sub validateDate {
    VALIDATE-DATE: {
        $date = <STDIN>;
        if ($date !~ 
             /^(19|20)\d\d([-  /.])(0[1-9]|1[012])\2(0[1-9]|[12][0-9]|3[01])$/) {
            print " $userStart in incorrect format, should be yyyy-mm-dd\n"
            print " Would you like to re-enter a date press (Y or N)?\n";
            my $choice = <STDIN>;
            if ($choice =~ /[Yy]/) {
                redo VALIDATE_DATE;
            } else {
                exit;
            }
        }
        return $date;
    }
}

However , when I run it I get this error:

Unmatched [ in regex; marked by <-- HERE in m/^(19|20)\d\d([ <-- HERE - / at common_subs.pl line 60. Compilation failed in require at add.pl line 7.

Error says that there is an unmatched ' [ ' but this isn't the case. I assume its something wrong with the regexp itself ? I am calling the sub from a separate file.

Answer 1

First, escape /. / is used as delimiter for regular expression literal. / inside that literal should be escaped.

/^(19|20)\d\d([-  \/.])(0[1-9]|1[012])\2(0[1-9]|[12][0-9]|3[01])$/
#                 ^^

or use different delimiter:

m{^(19|20)\d\d([- /.])(0[1-9]|1[012])\2(0[1-9]|[12][0-9]|3[01])$}

---

The following line is missing terminating ;:

print " $userStart in incorrect format, should be yyyy-mm-dd\n";
#                                                              ^

Answer 2

In fact your regex indeed is missing a ].

Since / is the delimiter symbol, the perl compiler stops at the unescaped slash inside your regex, so that you regex effectively looks like this:

/^(19|20)\d\d([-  /

which obviously is missing the ] ;-)

Either use a different delimiter symbol (often people use ! or something similar) or simply escape the slash.