Re: Am I on the pipe, or what?

Perl is seeing the pipe as alternation to nothing, i.e. 'either this or anything else'. Here are the details from a debugging perl (5.8.0-RC1):

$ perl -Dr pipe.pl
Omitting $` $& $' support.

EXECUTING...

Compiling REx `lo/gos'
size 4 Got 36 bytes for offset annotations.
first at 1
rarest char / at 2
   1: EXACT <lo/gos>(4)
   4: END(0)
anchored `lo/gos' at 0 (checking anchored isall) minlen 6 
Offsets: [4]
    1[6] 0[0] 0[0] 7[0] 
Guessing start of match, REx `lo/gos' against `lo/gou'...
Did not find anchored substr `lo/gos'...
Match rejected by optimizer
Freeing REx: `lo/gos'
Compiling REx `lo/gou'
size 4 Got 36 bytes for offset annotations.
first at 1
rarest char / at 2
   1: EXACT <lo/gou>(4)
   4: END(0)
anchored `lo/gou' at 0 (checking anchored isall) minlen 6 
Offsets: [4]
    1[6] 0[0] 0[0] 7[0] 
Guessing start of match, REx `lo/gou' against `lo/gou'...
Found anchored substr `lo/gou' at offset 0...
Guessed: match at offset 0
lo/gou
Freeing REx: `lo/gou'
Compiling REx `lo/gw|'
size 7 Got 60 bytes for offset annotations.

   1: BRANCH(5)
   2:   EXACT <lo/gw>(7)
   5: BRANCH(7)
   6:   NOTHING(7)
   7: END(0)
minlen 0 
Offsets: [7]
    0[0] 1[5] 0[0] 0[0] 6[1] 6[0] 7[0] 
Matching REx `lo/gw|' against `lo/gou'
  Setting an EVAL scope, savestack=16
   0 <> <lo/gou>          |  1:  BRANCH
  Setting an EVAL scope, savestack=22
   0 <> <lo/gou>          |  2:    EXACT <lo/gw>
                              failed...
   0 <> <lo/gou>          |  6:    NOTHING
   0 <> <lo/gou>          |  7:    END
Match successful!
lo/gw|
Freeing REx: `lo/gw|'
Compiling REx `lo/gon'
size 4 Got 36 bytes for offset annotations.
first at 1
rarest char / at 2
   1: EXACT <lo/gon>(4)
   4: END(0)
anchored `lo/gon' at 0 (checking anchored isall) minlen 6 
Offsets: [4]
    1[6] 0[0] 0[0] 7[0] 
Guessing start of match, REx `lo/gon' against `lo/gou'...
Did not find anchored substr `lo/gon'...
Match rejected by optimizer
Freeing REx: `lo/gon'
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After Compline,
Zaxo

Comment on Re: Am I on the pipe, or what? Download Code

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Re: Re: Am I on the pipe, or what? by flounder99 (Friar) on Jul 10, 2002 at 04:40 UTC
If you don't want to compile a debugging version use YAPE::Regex::Explain use strict; use YAPE::Regex::Explain; print YAPE::Regex::Explain->new(qr'lo/gw\|')->explain(); __OUTPUT__ The regular expression: (?-imsx:lo/gw\|) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- lo/gw 'lo/gw' ---------------------------------------------------------------------- \| OR ---------------------------------------------------------------------- ) end of grouping ---------------------------------------------------------------------- [download] -- flounder	[reply] [d/l]

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Re: Re: Am I on the pipe, or what?
by flounder99 (Friar) on Jul 10, 2002 at 04:40 UTC

YAPE::Regex::Explain

use strict;
use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(qr'lo/gw|')->explain();

__OUTPUT__

The regular expression:

(?-imsx:lo/gw|)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  lo/gw                    'lo/gw'
----------------------------------------------------------------------
 |                        OR
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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flounder

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