As with the OP's version that you based yours on, this fails several of these tests:

my @tests = (
    # $string, $pos, $expected, $description
    [ "\nString\n", 2, 6, 'Surrounded' ],
    [ "String\n",   2, 6, 'No first \n' ],
    [ "\nString",   2, 6, 'No last \n' ],
    [ "String",     2, 6, 'No \n' ],
    [ "",           0, 0, 'Blank' ],
);

[download]

Since the OP's version failed those as well, this is understandable. Obviously even more tests would be needed, but this was meant as more of a sanity check than anything.

Performance-wise, here's where your solution fits in:

                Rate     op_ver      daxim    rlindex cur_strlen
op_ver      564186/s         --       -23%       -66%       -86%
daxim       737063/s        31%         --       -56%       -81% <-- H
+ERE
rlindex    1677856/s       197%       128%         --       -57%
cur_strlen 3932672/s       597%       434%       134%         --

[download]

Of course, I am not sure what sort of performance impact (for better or worse) a fixed version of your code would have. Complete code for my test and benchmark suite is in my comment, if you want to have a go with it yourself.

not ok 1 - daxim: Surrounded
#   Failed test 'daxim: Surrounded'
#   at /home/ryan/src/perlmonks/subline.pl line 37.
#          got: '7'
#     expected: '6'
Use of uninitialized value $prev in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
not ok 2 - daxim: No first \n
#   Failed test 'daxim: No first \n'
#   at /home/ryan/src/perlmonks/subline.pl line 37.
#          got: '7'
#     expected: '6'
Use of uninitialized value $prev in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
not ok 3 - daxim: No last \n
#   Failed test 'daxim: No last \n'
#   at /home/ryan/src/perlmonks/subline.pl line 37.
#          got: '1'
#     expected: '6'
Use of uninitialized value $prev in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
Use of uninitialized value $next in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
not ok 4 - daxim: No \n
#   Failed test 'daxim: No \n'
#   at /home/ryan/src/perlmonks/subline.pl line 37.
#          got: '0'
#     expected: '6'
Use of uninitialized value $prev in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
Use of uninitialized value $next in subtraction (-) at /home/ryan/src/
+perlmonks/subline.pl line 64.
ok 5 - daxim: Blank

[download]
use strict; use warnings; omitted for brevity.

In reply to Re^2: Finding length of line if have any position of any char inside line by rjt
in thread Finding length of line if have any position of any char inside line by phoenix007

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