Your regex  s/[\s]+//mgx deletes all whitespace, and you don't want that -- you want to preserve the spaces that separate the four strings on the line that starts with ">".

(I could also point out that in your regex, the square brackets and "m" and "x" modifiers could all be removed and it would do the same thing it does now -- including them has no effect at all in this case. Of course, this also means they do no harm, but if you don't understand why they do nothing in this case, it wouldn't hurt you to try reading the perlre manual page.)

As GrandFather points out, you only want to eliminate the extra "\n" characters. The specific output that you say you want (with the initial "\n" still intact) would come out with just this: 

s/\n\s*/\n/g;  # every string of \n plus 0-or-more whitespace --> sing
+le \n

[download]
(updated to emulate GrandFather's handling of "blank" lines that contain just spaces and/or tabs)

In reply to Re: Removing empty line(s) with regex in a multiple strings in a variable by graff
in thread Removing empty line(s) with regex in a multiple strings in a variable by monkfan

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.