gjb is right -- if the problem is that the hash key contains special characters but you want these to be treated as literals (i.e "$" matches an actual dollar-sign character in the string), then just say  s/\Q$item\E/$newitem/ (you don't need to put "quotemeta" operators around the right-side of the expression).

On the other hand, sometimes it's handy to make use of metacharacters, and always applying quotemeta operators would make this impossible. For example maybe the string is full-of-hyphenated-forms, and you just want to replace the hyphens with spaces - without removing "dashes" that operate as punctuation (having spaces around them instead of letters) - so a single regex with special characters is just what you want: 

 s/(?<=[a-z])-(?=[a-z])/ /g;

[download]
In this case, the trick is to make sure that you get all the magical characters you want into the regex exactly as they should be, without them getting interpolated into something else -- and you have to make sure that things like dollar and percent signs that need to be treated literally are all provided with literal backslash escapes. For example: 
my %replacement;

$replacement{'\$34\.50'} = '$17.25';
# ... key is match, value is replacement

for my $item ( keys %replacement ) {
    s/$item/$replacement{$item}/g;
}

[download]
Given a framework like that, do be careful about items that might interfere with one another (such that the final result might depend on the order in which edits are applied). This is the sort of thing where an AoA might be better than a hash: 
my $replacements = 
 [
   ['S\&O 400', 'S&P 500'],
   ['\b400\b', '200'],
#   ... (or read these match/replace literals from a file)
 ]

# this provides a stable, consistent order of application

for my $edit ( @$replacements ) {
    s/$$edit[0]/$$edit[1]/;
}

[download]

In reply to Re: Performing substitutions on lines with special characters by graff
in thread Performing substitutions on lines with special characters by wouldbewarrior

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.