Multiline issue regarding index() function when matching ^ and/or $

[jurvei]

When using '-re' to match a regex, there is an issue regarding the used index() function and matching ^ or $.

Example (simplified, but represents the code of Example.pm:759-785

my $string = "test\r\ntest-end-test\r\nend";
my $pattern = qr/^end$/m;
if (my @matchlist = ($string =~ m/($pattern)/)) {
    # match successful => the "end" at the end of the string is matched and stored in @matchlist

    # but now you are using index() to determine the position... which will give you the position of the "end" string at "test-end-test", NOT the matched "end" at the end of the string
    my $start = index $string, $matchlist[0];

    # so in the end, $before and $after are wrong
    my $before = substr $string, 0, $start;
    my $after = substr $string, $start + length($matchlist[0]);

    print "Before: $before\n";
    print "After: $after\n";
}

String:

test
test-end-test
end

Output:

Before: test
test-
After: -test
end

Expected output:

Before: test
test-end-test

After:

The code used in v1.25 was not using index() and seems to work as expectd.

@matchlist = ( ${*$exp}{exp_Accum} =~ m/$pattern->[2]()/m );
( $match, $before, $after ) = ( $&, $`, $' );

[Karl-Hungus-Autobahn]

I am, too, suffering from this problem (see details below), the patched version of Expect.pm provided in this thread here above solves it for me. Is there a reason, why the patch was not considered so far? It would be greatly appreciated.

Relevant debug output, notice the unwanted residue in "After match string":

spawn id(3): Does `\r\n\r\n{master:0}\r\nroot@router> \r\n\r\n{master:0}\r\nroot@router'
match:
  pattern #1: -re `(?^:[\\r\\n]+[^\\r\\n<]+[#>%] ?$)'? No.


spawn id(3): Does `\r\n\r\n{master:0}\r\nroot@router> \r\n\r\n{master:0}\r\nroot@router> '
match:
  pattern #1: -re `(?^:[\\r\\n]+[^\\r\\n<]+[#>%] ?$)'? YES!!
    Before match string: `\r\n\r\n{master:0}'
    Match string: `\r\nroot@router> '
    After match string: `\r\n\r\n{master:0}\r\nroot@router> '
    Matchlist: ()

see also https://stackoverflow.com/questions/79247491/solved-expect-module-end-of-string-is-correctly-matched-but-characters-remain