#!/usr/bin/perl --

use warnings;
use strict;

use re 'debug';

my $chr = "this and that";
$chr =~ s/(this|that)|(\w+)/$1\U$2/g; #error reported
print "$chr\n";
__END__

[download]
Compiling REx `(this|that)|(\w+)'
size 19 Got 156 bytes for offset annotations.

   1: BRANCH(12)
   2:   OPEN1(4)
   4:     BRANCH(7)
   5:       EXACT <this>(10)
   7:     BRANCH(10)
   8:       EXACT <that>(10)
  10:   CLOSE1(19)
  12: BRANCH(19)
  13:   OPEN2(15)
  15:     PLUS(17)
  16:       ALNUM(0)
  17:   CLOSE2(19)
  19: END(0)
minlen 1 
Offsets: [19]
    0[0] 1[1] 0[0] 1[1] 2[4] 0[0] 6[1] 7[4] 0[0] 11[1] 0[0] 12[1] 13[1
+] 0[0] 16[1] 14[2] 17[1] 0[0] 18[0] 
Matching REx `(this|that)|(\w+)' against `this and that'
  Setting an EVAL scope, savestack=5
   0 <> <this and tha>    |  1:  BRANCH
  Setting an EVAL scope, savestack=15
   0 <> <this and tha>    |  2:    OPEN1
   0 <> <this and tha>    |  4:    BRANCH
  Setting an EVAL scope, savestack=25
   0 <> <this and tha>    |  5:      EXACT <this>
   4 <this> < and tha>    | 10:      CLOSE1
   4 <this> < and tha>    | 19:      END
Match successful!
Matching REx `(this|that)|(\w+)' against ` and that'
  Setting an EVAL scope, savestack=25
   4 <this> < and tha>    |  1:  BRANCH
  Setting an EVAL scope, savestack=35
   4 <this> < and tha>    |  2:    OPEN1
   4 <this> < and tha>    |  4:    BRANCH
  Setting an EVAL scope, savestack=45
   4 <this> < and tha>    |  5:      EXACT <this>
                                failed...
   4 <this> < and tha>    |  8:      EXACT <that>
                                failed...
  Clearing an EVAL scope, savestack=35..45
   4 <this> < and tha>    | 13:    OPEN2
   4 <this> < and tha>    | 15:    PLUS
                           ALNUM can match 0 times out of 2147483647..
+.
  Setting an EVAL scope, savestack=35
                              failed...
  Clearing an EVAL scope, savestack=25..35
  Setting an EVAL scope, savestack=25
   5 <this > <and tha>    |  1:  BRANCH
  Setting an EVAL scope, savestack=35
   5 <this > <and tha>    |  2:    OPEN1
   5 <this > <and tha>    |  4:    BRANCH
  Setting an EVAL scope, savestack=45
   5 <this > <and tha>    |  5:      EXACT <this>
                                failed...
   5 <this > <and tha>    |  8:      EXACT <that>
                                failed...
  Clearing an EVAL scope, savestack=35..45
   5 <this > <and tha>    | 13:    OPEN2
   5 <this > <and tha>    | 15:    PLUS
                           ALNUM can match 3 times out of 2147483647..
+.
  Setting an EVAL scope, savestack=35
   8 <his and> < that>    | 17:      CLOSE2
   8 <his and> < that>    | 19:      END
Match successful!
Use of uninitialized value in concatenation (.) or string at 2 line 9.
Matching REx `(this|that)|(\w+)' against ` that'
  Setting an EVAL scope, savestack=35
   8 <his and> < that>    |  1:  BRANCH
  Setting an EVAL scope, savestack=45
   8 <his and> < that>    |  2:    OPEN1
   8 <his and> < that>    |  4:    BRANCH
  Setting an EVAL scope, savestack=55
   8 <his and> < that>    |  5:      EXACT <this>
                                failed...
   8 <his and> < that>    |  8:      EXACT <that>
                                failed...
  Clearing an EVAL scope, savestack=45..55
   8 <his and> < that>    | 13:    OPEN2
   8 <his and> < that>    | 15:    PLUS
                           ALNUM can match 0 times out of 2147483647..
+.
  Setting an EVAL scope, savestack=45
                              failed...
  Clearing an EVAL scope, savestack=35..45
  Setting an EVAL scope, savestack=35
   9 <his and > <that>    |  1:  BRANCH
  Setting an EVAL scope, savestack=45
   9 <his and > <that>    |  2:    OPEN1
   9 <his and > <that>    |  4:    BRANCH
  Setting an EVAL scope, savestack=55
   9 <his and > <that>    |  5:      EXACT <this>
                                failed...
   9 <his and > <that>    |  8:      EXACT <that>
  13 <his and that> <>    | 10:      CLOSE1
  13 <his and that> <>    | 19:      END
Match successful!
String too short [regexec_flags]...
Match failed
Freeing REx: `"(this|that)|(\\w+)"'

[download]

In reply to Re: why such an error happened? by Anonymous Monk
in thread why such an error happened? by lightoverhead

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