Don't you mean

/\Q$foo\E/ and print "$&\n"; s/\Q$foo\E/XYZ/;

Using -w would have helped you figure it out.

Update: oh right, deliberate tyops. Well, now that I've really thought about it... this is what is going on. The line

/\Q$fooE/ and print "$&\n";

given that $fooE is not defined is the same thing as

/\Q/ and print "$&\n";

which is the same thing as

// and print "$&\n";

Which is the same thing as finding the same thing as the last successful match. This also applies to the s expression, which is why your bar appears to be magically transmuting itself into XYZ.

That's not a bug, that's a feature.


--
g r i n d e r

In reply to Re:x4 Regex Grumblings (Variable Interpolation) by grinder
in thread Regex Grumblings (Variable Interpolation) by tadman

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.