You may want to take a look at perlre and perlretut. I usually pick something such as below (admittedly picked it up from Perl Best Practices by Damian Conway). I like to use the 'xms' modifiers: 

my $line = qr{
    \A        # Start of string
    \s*        # Leading blanks
    \w+        # Key
    \s*
    \w+        # Value
    \s*        # Trailing blanks
    \z        # End of string
}xms;

[download]

Alternatively, I use Regexp::Common as well if I want to build something up from components. It's not really what you were asking, but it may be handy.

In reply to Re: how to write a multi-line regex by rkrieger
in thread how to write a multi-line regex by zerocred

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.