Matched elements using regex in Perl

Question

I have a hash which contains a regular expression: the number of matches to be captured in it and variables and their position of match. For example:

my %hash = (
    reg_ex => 'Variable1:\s+(.*?)\s+\n\s+Variable2:\s+(.*?)\s+\n',
    count => 2,
    Variable1 => 1,
    Variable2  => 2,
);

I am going to use this regex in some other part of code where I will be just giving say $to_be_matched_variable =~ /$hash{reg_ex}/ and we obtain the required matches here in $1, $2, ...

I need to use the value of the key Variable1, which indicates the number of the match to be used in place where we normally use $1.

I tried giving $.$hash{Variable1} and $,$hash{Variable1}. I am not able to find how to frame something that will be equivalent to $1, $2...

This smells like something else is wrong with your architecture. What task are you trying to accomplish? — brian d foy
– brian d foy, Commented Apr 8, 2009 at 15:28
I'd suggest having reg_ex => qr/.../, so the whole thing is a bit clearer (IMO) — Tanktalus
– Tanktalus, Commented Apr 15, 2009 at 21:10

dreamlax · Accepted Answer · 2009-04-08 09:43:42Z

7

Try:

(my @ArrayOfMatches) = $to_be_matched_variable =~ /$hash{reg_ex}/;

my $Variable1 = $ArrayOfMatches[$hash{Variable1}];

edited Apr 8, 2009 at 9:43

answered Apr 8, 2009 at 8:40

dreamlax

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2 Comments

jpalecek Over a year ago

AFAIK, this doesn't work - the global match returns all matches of all parentheses in the string. Without /g, it would return ($1, $2, ...) as the OP needed.

dreamlax Over a year ago

Yeah, whoops! I knew that too. I always type g out of habit and figure out later that it's not what I want!

innaM · Accepted Answer · 2009-04-08 08:59:05Z

4

Since you are already using a hash, you might as well use the builtin %+ which maps names to matches. Thus if you changed your regexes to named matching, you could easily use %+ to retrieve the matched parts.

$reg_ex = 'Variable1:\s+(?<foo>.*?)\s+\n\s+Variable2:\s+(?<bar>.*?)\s+\n';

After a successful match, %+ should have the keys foo and bar and the values will correspond to what was matched.

Thus your original hash could be changed to something like this:

my %hash = (
    reg_ex => 'Variable1:\s+(?<foo>.*?)\s+\n\s+Variable2:\s+(?<bar>.*?)\s+\n',
    groups => [ 'foo', 'bar' ],
);

answered Apr 8, 2009 at 8:59

innaM

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1 Comment

brian d foy Over a year ago

Named captures are the way to go if you can use Perl 5.10. There's a capture in Learning Perl about them. :)

Ingo · Accepted Answer · 2009-04-08 08:42:43Z

3

($1, $2, $3, ...., $9)[$hash{Variable1}]

answered Apr 8, 2009 at 8:42

Ingo

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2 Comments

dreamlax Over a year ago

Wow! How very implicit! How very Perl ;)

Ingo Over a year ago

yes, unlike MyFineArrayOfMatchesWhereIStoreMyMatchesYouKnow. :)

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