Can I use named groups in a Perl regex to get the results in a hash?


Question

Is it possible to perform a named-group match in Perl's regex syntax as with Python's? I always bind the $n values to proper names after matching, so I'd find it more convenient to do it in the regex itself if it's possible.

Python does it like so:

>>> import re
>>> regex = re.compile(r'(?P<count>\d+)')
>>> match = regex.match('42')
>>> print match.groupdict()
{'count': '42'}

I know the ?P indicates that it's a Python-specific regex feature, but I'm hoping it's in Perl in a different way or was added later on. Is there any way to get a result hash in a similar manner in Perl?

1
19
11/14/2008 3:09:20 AM

Accepted Answer

Perl uses (?<NAME>pattern) to specify names captures. You have to use the %+ hash to retrieve them.

$variable =~ /(?<count>\d+)/;
print "Count is $+{count}";

This is only supported on Perl 5.10 and higher though.

39
12/12/2008 11:47:01 PM

As of Perl 5.10, Perl regexes support some Python features, making them Python compatible regexes, I guess. The Python versions have the "P" in them, but all of these work in Perl 5.10. See the perlre documentation for the details:

Define a named capture buffer. Equivalent to (?<NAME>pattern).

(?P<NAME>pattern)

Backreference to a named capture buffer. Equivalent to \g{NAME}.

(?P=NAME)

Subroutine call to a named capture buffer. Equivalent to (?&NAME).

(?P>NAME)

Although I didn't add the Python-compatibility to the latest edition of Learning Perl, we do cover the new Perl 5.10 features, including named captures.


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