An s flag tells the regex to ignore line boundaries, which it won't do normally.

I wouldn't put it that way. /s makes newlines a valid match for ".". Moreover, perl normally does ignore internal line boundaries unless one tells it not to with /m. E.g. 

my $s = "a\nb\nc\n";
my @g   = map "[$_]", $s =~ /(.)$/g;
my @gs  = map "[$_]", $s =~ /(.)$/gs;
my @gm  = map "[$_]", $s =~ /(.)$/gm;
my @gsm = map "[$_]", $s =~ /(.)$/gsm;
print "g:   @g\n";
print "gs:  @gs\n";
print "gm:  @gm\n";
print "gsm: @gsm\n";
__END__
g:   [c]
gs:  [c] [
]
gm:  [a] [b] [c]
gsm: [a] [b] [c] [
]

[download]
Note in particular the case in which both /s and /m are used.

the lowliest monk

In reply to Re^2: Replacing everything in between using s///; by tlm
in thread Replacing everything in between using s///; by JayBee

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.