comment on

add use re 'debug'; and see for yourself :) its because you're using m//g, m//atchingglobal, global flag , matching globally affects the pos the regex starts matching from , see pos

code with m//globally perl -Mre=debug -le " $_=q{fakesite.com/f/files-url/blah.png}; if(m{fakesite.com.*}g){ warn 1; if(/files-url/g){ die 2 }} "

code without m//globally perl -Mre=debug -le " $_=q{fakesite.com/f/files-url/blah.png}; if(m{fakesite.com.*}){ warn 1; if(/files-url/){ die 2 }} "

run




$ perl -Mre=debug -le " $_=q{fakesite.com/f/files-url/blah.png}; if(m{
+fakesite.com.*}g){ warn 1; if(/files-url/g){ die 2
 }} "
Compiling REx "fakesite.com.*"
Final program:
   1: EXACT <fakesite> (4)
   4: REG_ANY (5)
   5: EXACT <com> (7)
   7: STAR (9)
   8:   REG_ANY (0)
   9: END (0)
anchored "fakesite" at 0 (checking anchored) minlen 12
Compiling REx "files-url"
Final program:
   1: EXACT <files-url> (5)
   5: END (0)
anchored "files-url" at 0 (checking anchored isall) minlen 9
Guessing start of match in sv for REx "fakesite.com.*" against "fakesi
+te.com/f/files-url/blah.png"
Found anchored substr "fakesite" at offset 0...
Guessed: match at offset 0
Matching REx "fakesite.com.*" against "fakesite.com/f/files-url/blah.p
+ng"
   0 <> <fakesite.c>         |  1:EXACT <fakesite>(4)
   8 <esite> <.com/f/fil>    |  4:REG_ANY(5)
   9 <site.> <com/f/file>    |  5:EXACT <com>(7)
  12 <e.com> </f/files-u>    |  7:STAR(9)
                                  REG_ANY can match 21 times out of 21
+47483647...
  33 <url/blah.png> <>       |  9:  END(0)
Match successful!
1 at -e line 1.
Freeing REx: "fakesite.com.*"
Freeing REx: "files-url"

$
$ perl -Mre=debug -le " $_=q{fakesite.com/f/files-url/blah.png}; if(m{
+fakesite.com.*}){ warn 1; if(/files-url/){ die 2 }
} "
Compiling REx "fakesite.com.*"
Final program:
   1: EXACT <fakesite> (4)
   4: REG_ANY (5)
   5: EXACT <com> (7)
   7: STAR (9)
   8:   REG_ANY (0)
   9: END (0)
anchored "fakesite" at 0 (checking anchored) minlen 12
Compiling REx "files-url"
Final program:
   1: EXACT <files-url> (5)
   5: END (0)
anchored "files-url" at 0 (checking anchored isall) minlen 9
Guessing start of match in sv for REx "fakesite.com.*" against "fakesi
+te.com/f/files-url/blah.png"
Found anchored substr "fakesite" at offset 0...
Guessed: match at offset 0
Matching REx "fakesite.com.*" against "fakesite.com/f/files-url/blah.p
+ng"
   0 <> <fakesite.c>         |  1:EXACT <fakesite>(4)
   8 <esite> <.com/f/fil>    |  4:REG_ANY(5)
   9 <site.> <com/f/file>    |  5:EXACT <com>(7)
  12 <e.com> </f/files-u>    |  7:STAR(9)
                                  REG_ANY can match 21 times out of 21
+47483647...
  33 <url/blah.png> <>       |  9:  END(0)
Match successful!
1 at -e line 1.
Guessing start of match in sv for REx "files-url" against "fakesite.co
+m/f/files-url/blah.png"
Found anchored substr "files-url" at offset 15...
Starting position does not contradict /^/m...
Guessed: match at offset 15
2 at -e line 1.
Freeing REx: "fakesite.com.*"
Freeing REx: "files-url"

$
[download]

shorter one

$ perl -Mre=debug -le "$f=123; $f=~/^.*/g; warn pos $f; $f=~ /\d/g; wa
+rn pos $f; "
Compiling REx "^.*"
Final program:
   1: BOL (2)
   2: STAR (4)
   3:   REG_ANY (0)
   4: END (0)
anchored(BOL) minlen 0
Compiling REx "\d"
Final program:
   1: DIGIT (2)
   2: END (0)
stclass DIGIT minlen 1
Matching REx "^.*" against "123"
   0 <> <123>                |  1:BOL(2)
   0 <> <123>                |  2:STAR(4)
                                  REG_ANY can match 3 times out of 214
+7483647...
   3 <123> <>                |  4:  END(0)
Match successful!
3 at -e line 1.
Warning: something's wrong at -e line 1.
Freeing REx: "^.*"
Freeing REx: "\d"

$ perl -Mre=debug -le "$f=123; $f=~/^.*/; warn pos $f; $f=~ /\d/; warn
+ pos $f; "
Compiling REx "^.*"
Final program:
   1: BOL (2)
   2: STAR (4)
   3:   REG_ANY (0)
   4: END (0)
anchored(BOL) minlen 0
Compiling REx "\d"
Final program:
   1: DIGIT (2)
   2: END (0)
stclass DIGIT minlen 1
Matching REx "^.*" against "123"
   0 <> <123>                |  1:BOL(2)
   0 <> <123>                |  2:STAR(4)
                                  REG_ANY can match 3 times out of 214
+7483647...
   3 <123> <>                |  4:  END(0)
Match successful!
Warning: something's wrong at -e line 1.
Matching REx "\d" against "123"
Matching stclass DIGIT against "123" (3 bytes)
   0 <> <123>                |  1:DIGIT(2)
   1 <1> <23>                |  2:END(0)
Match successful!
Warning: something's wrong at -e line 1.
Freeing REx: "^.*"
Freeing REx: "\d"

$
[download]

In reply to Re: Why this Simple REGEX does Not Match? (re debug match globally pos) by Anonymous Monk
in thread Why this Simple REGEX does Not Match? by mmartin

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