regexp "?" delimiter

[cmic]

The following code (using Perl 5.24 on Debian) yields this error:
syntax error at ./regexp.pl line xx, near "if ?"

my ($DICT, $first, $last);
open $DICT, "<", "/usr/share/dict/words";
while (<$DICT>) {
#FIXME
    $first = $1 if ?(^neuro.*)?;  #  <- syntax error here 
    $last = $1 if  /(^neuro.*)/;
}
close $DICT;
print "first : $first, last : $last \n";
print "-" x 10, "\n";
#

Is it a deprecated usage of the "?" delimiter ?
Or what ?

[choroba]

Please, edit your node and move the question up away from the signature part. Some monks have turned signature display off.

The ?...? delimiter should be written m?...? starting with 5.22.

I'd extend the original code with

use Syntax::Construct qw{ ?? };

if it were still running in the original environment. But adding the m would work in the old versions, too, so it's an unnecessary step.

[Corion]

The support for ?PATTERN? matching was removed in Perl 5.22.0, four years ago. You will need to use a matching operator and operand, like $_ =~ ?(^neuro.*)?. You will need to use a prefixed m, as choroba and Eily show.

In the perldelta, you can read what changed between each version of Perl 5.

[Eily]

To use a character as a delimiter, you have to prepend the corresponding operator to indicate what it is the delimiter of, q for a single quote string, y for a transliteration, m for a matching operation (regex)... The trick is, when perl sees / in a place where it could expect a regex, is guesses that you meant m/. So /(^neuro.*)/ is actually m/(^neuro.*)/ where m means "make / the delimiter for a match operation".

So you should use m?(^neuro.*)?

Edit: oh I thought the m had always been required except for //, turns out there used to be an exception for ?? as well.

[cmic]

Thanks Eily for clear explanations.
-- cmic. Retired Sysadmin....