in reply to
Re: Why \n matches but not $^? (weight)
in thread Why \n matches but not $^?
If 'm' as flag causes ^ and $ to gain magic as in
m Treat string as multiple lines. That is, change "^" and "$" from
matching the start or end of the string to matching the start or
end of any line anywhere within the string.
and $ matches end-of-line (or before newline) as in
$ Match the end of the line (or before newline at the end)
It might be arguable that the newline would be matched by $ in
$ perl -Mre=debug -wle'"ABC\nDEF" =~ m/C(?:$)^D/m'
Freeing REx: `","'
Compiling REx `C(?:$)^D'
size 7 Got 60 bytes for offset annotations.
first at 1
rarest char D at 1
1: EXACT <C>(3)
3: MEOL(4)
4: MBOL(5)
5: EXACT <D>(7)
7: END(0)
anchored "CD" at 0 (checking anchored) minlen 2
Offsets: [7]
1[1] 0[0] 5[1] 7[1] 8[1] 0[0] 9[0]
Omitting $` $& $' support.
EXECUTING...
Guessing start of match, REx "C(?:$)^D" against "ABC
DEF"...
Did not find anchored substr "CD"...
Match rejected by optimizer
Freeing REx: `"C(?:$)^D"'
I understand that it doesn't. Making the newline explicit as in tye's example does
$ perl -Mre=debug -wle'"ABC\nDEF" =~ m/C(?:$)$\?^D/m'
Freeing REx: `","'
Omitting $` $& $' support.
EXECUTING...
Compiling REx `C(?:$)
?^D'
size 11 Got 92 bytes for offset annotations.
first at 1
rarest char D at 0
rarest char C at 0
1: EXACT <C>(3)
3: MEOL(4)
4: CURLY {0,1}(8)
6: EXACT <\n>(0)
8: MBOL(9)
9: EXACT <D>(11)
11: END(0)
anchored "C"$ at 0 floating "D" at 1..2 (checking floating) minlen 2
Offsets: [11]
1[1] 0[0] 5[1] 8[1] 0[0] 7[1] 0[0] 9[1] 10[1] 0[0] 11[0]
Guessing start of match, REx "C(?:$)
?^D" against "ABC
DEF"...
Found floating substr "D" at offset 4...
Found anchored substr "C"$ at offset 2...
Starting position does not contradict /^/m...
Guessed: match at offset 2
Matching REx "C(?:$)
?^D" against "C
DEF"
Setting an EVAL scope, savestack=6
2 <AB> <C
DEF> | 1: EXACT <C>
3 <ABC> <
DEF> | 3: MEOL
3 <ABC> <
DEF> | 4: CURLY {0,1}
EXACT <\n> can match 1 times out of 1...
Setting an EVAL scope, savestack=6
4 <ABC
> <DEF> | 8: MBOL
4 <ABC
> <DEF> | 9: EXACT <D>
5 <ABC
D> <EF> | 11: END
Match successful!
Freeing REx: `"C(?:$)\n?^D"'
