The  /g modifier can simply not be used with  qr// to build a regex object. It can only be used with the  m// and  s/// operators; interpolation of a regex object into one of these (or literals) is your only hope. Please see the discussion of  qr// in Regexp Quote-Like Operators in perlop and note the available modifiers. See also the discussions of  m// and  s/// (and their available modifiers) in the same section.

Update:

... I also just noticed that ... the 'x' option doesn't seem to work ...
It works just fine: 
c:\@Work\Perl>perl -wMstrict -le
"my $s = 'xxxfoooooyyy';
 ;;
 $s =~ /(?x) ( f o o + ) /;
 print qq{'$1'};
"
'fooooo'

[download]

Give a man a fish:  <%-{-{-{-<

In reply to Re: 'g' flag w/'qr' by AnomalousMonk
in thread 'g' flag w/'qr' by perl-diddler

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.