Here is a safe, fast, eval-less method that doesn't use s/// :-) 

sub munge {
    my ($str, $pat, $repl) = @_;

    while ($str =~ /$pat/g) {
        my $temp = $repl;
        for (1..$#+) {
            while ( (my $x = index $temp, "\$$_") >= 0) {
                substr ($temp, $x, length($_)+1) = $$_;
            }
        }
        my $pos = pos $str;
        my $offset = $+[$#+]-$-[0];
        substr($str, $pos-$offset, $offset) = $temp;
        pos($str) = $pos - $offset + length($temp);
    }

    return $str;
}

# Here's an example:
print "#";
print munge('aaaababbaabbbbabab', '(a)(b+)', ' $2*$1 ');
print "#";

[download]

In reply to Re: $1 in variable regex replacement string by jryan
in thread $1 in variable regex replacement string by dvergin

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.