Of course if you had meant the string $to_replace is an actual regex to match against, you're better off using the qr operator:
I don't get this point. You started off that section with: 
$to_replace='some_string';
$my_string=~ s/$to_replace/$better_data/;

[download]
and doomed this catastrophically unsafe, because $to_replace may actually contain characters that have a special meaning.

But if $to_replace is actually a regexp, the premises is gone -- any special characters are intentional. In fact, it's quite fine in that case to use the above.

In reply to Re: Common Perl Pitfalls by JavaFan
in thread Common Perl Pitfalls by Joe_

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.