regexp help -- grab almost a whole string

tdruttenberg has asked for the wisdom of the Perl Monks concerning the following question:

My string is in this format

'DHEC(optional dot)(unspecified number of alphanumerics'

for example:

$if_descr = 'DHEC.177628'
or
$if_descr = 'DHEC177628'

I want to grab everything but the dot and assign it to $circuit_id. I've been trying to use a lookaround to grab the string before and after the dot, but have been unsuccessful.

Here is the latest thing I tried:

($circuit_id) = $if_descr =~ /
             .*?
             (
                DHEC
                  (?:
                    \.?
                  )
                [^\s]+
             )
/xims;
[download]

I've also tried simply

($circuit_id) = $if_descr =~ /.*?
             (
                DHEC
                  (?=\.)
                [^\s]+
             )
/xims;
[download]

No dice.

How do I do this?

TDR

Comment on regexp help -- grab almost a whole string Select or Download Code

Replies are listed 'Best First'.
Re: regexp help -- grab almost a whole string by ikegami (Patriarch) on May 19, 2009 at 18:08 UTC
`my $circuit_id = ( $if_descr =~ /([^.])(?:\.(.))?/ ? $1 . (defined($2) ? $2 : '') : undef );` [download] But it can be shortened to `(my $circuit_id = $if_descr) =~ s/\.//;` [download]	[reply] [d/l] [select]
Re: regexp help -- grab almost a whole string by moritz (Cardinal) on May 19, 2009 at 18:06 UTC
`if ($if_descr =~ m/DHEC\.?(\w+)/) { print "'$1'\n"; $circuite_id = $1; }` [download] Nice and simple, no need for look-arounds whatsoever.	[reply] [d/l]
Re: regexp help -- grab almost a whole string by kennethk (Abbot) on May 19, 2009 at 18:09 UTC
Since your desired capture is essentially two strings, you would have to join the two halves together after the capture. How about: `$circuit_id = join q{}, $if_descr =~ /([^.])\.?([^.])/;` Easier, though, is just to do: `$circuit_id = $if_descr; $circuit_id ~= s/\.//;` [download]	[reply] [d/l] [select]
Re: regexp help -- grab almost a whole string by tdruttenberg (Initiate) on May 19, 2009 at 19:31 UTC
What I need is a single regexp that will get the result the first time. It is to be returned from a subroutine kinda like this: `sub get_regexp { if ($blah) $regexp = qr {}; elsif ($blahblah) $regexp = qr {}; }` [download] calling program `$REGEXP = get_regexp($ip); ($circuit_id) = $if_descr =~ $REGEXP;` [download] I want to get the correct result with one regexp without having to do any cleanup after the fact (ie removing the dot in a different step). There must be a way to do this? If not, I will simply leave the dot in. TDR	[reply] [d/l] [select]
Re^2: regexp help -- grab almost a whole string by kennethk (Abbot) on May 19, 2009 at 19:58 UTC
Since your strings are separated, they must be captured in separate buffers and there is no way to join them with just a matching regular expression. If you change the calling program to implement the join solution I suggested above, it will not break existing behavior, except that failed matches will store a null string ("") in $circuit_id in place of an undef (both of which still evaluate false). If you cannot change the calling program, then I see no solution. `$REGEXP = get_regexp($ip); $circuit_id = join q{}, $if_descr =~ $REGEXP;` [download]	[reply] [d/l]
Re^2: regexp help -- grab almost a whole string by grizzley (Chaplain) on May 20, 2009 at 05:57 UTC
I think I did similar mistake while designing new test system at work. The assumption was, that every value can be tested and checked with a regexp. `$regexp = ...; if($value !~ /$regexp/) { $err .= "wrong value ($value)" }` [download] Everything was fine. And then came the issue with integer range, i.e. value must be integer between 0 and 12800... Now I think about redesigning the engine to accept sub reference instead of regexp: `$subref = ...; if(! &$subref($value)) { $err .= "wrong value ($value)" }` [download] because the only reasonable way of fixing it is to abandon assumption about "regexp can match even the universe" (pity, I like regexps...)	[reply] [d/l] [select]
Re^2: regexp help -- grab almost a whole string by Polyglot (Chaplain) on May 20, 2009 at 03:27 UTC
I'm not certain why it must be a "single regexp", but this will do the job in a single line of execution: if ($if_desc =~ /(DHEC)\.?(\w+)/) {$circuit_id = "$1$2"}; Would this satisfy your requirement? Blessings, ~Polyglot~	[reply]