Sometimes it's better to extract out what you want rather than trying to split out what you don't want. (\K available with Perl 5.10+.) 

>perl -wMstrict -le
"my $str = 'Iteration {Applied Field}  {Total Energy}  {Foo}  {  a b  
+ c d  }  Mx';
 ;;
 my $rx_word  = qr{ [[:alnum:]]+ }xms;
 my $rx_curly = qr{ { \s* \K  $rx_word (?: \s+ $rx_word)*  (?= \s* }) 
+}xms;
 ;;
 my @fields = $str =~ m{ $rx_curly | $rx_word }xmsg;
 printf qq{'$_' } for @fields;
"
'Iteration' 'Applied Field' 'Total Energy' 'Foo' 'a b   c d' 'Mx'

[download]

In reply to Re: Splitting string using two overlapping patterns by AnomalousMonk
in thread Splitting string using two overlapping patterns by kpr

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.