$text_1 = "abc\nd";
$text_1 =~ m/.*(.|\n)/;
...
Should print d

A narration of  m/.*(.|\n)/ might be:

1. .* From the start of the string, grab as much as possible of anything that's not a newline (no /s modifier for dot);
2. (.|\n) Then match and capture the first thing that's either not-a-newline or a newline.

Looked at this way, the only thing that could possibly be captured in the given string would be a newline.

Indeed, if your regex has no operator introduced after Perl version 5.6, this kind of narration is what YAPE::Regex::Explain will give you:

c:\@Work\Perl\monks>perl -wMstrict -le
"use YAPE::Regex::Explain;
 print YAPE::Regex::Explain->new(qr/.*(.|\n)/)->explain();
"
The regular expression:

(?-imsx:.*(.|\n))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    .                        any character except \n
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    \n                       '\n' (newline)
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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(There are newer and better regex parser/explainers around, but I like this one, limited as it is, for its explanatory style.)