The regex word boundary meta character, \b, does not seem to match start of string if the first word character of the string is escaped. Is this expected behavior?

Here is an example of the behavior in question:

apocalypse.OCF [178] perl5.8.5 -e 'my $s = "\@testing"; 
$s =~ s/\b\@testing\b//i; print "$s\n";' 

@testing

apocalypse.OCF [179] perl5.8.5 -e 'my $s = "+testing"; 
$s =~ s/\b\+testing\b//i; print "$s\n";' 

+testing

apocalypse.OCF [180] perl5.8.5 -e 'my $s = "testing"; 
$s =~ s/\btesting\b//i; print "$s\n";' 


apocalypse.OCF [181]

[download]

For now I'm using (\b|^)\@testing(\b|$) as a workaround, but this behavior seems at odds with perlre, which states:

A word boundary ( \b ) is defined as a spot between two characters that has a \w on one side of it and and a \W on the other side of it (in either order), counting the imaginary characters off the beginning and end of the string as matching a \W .

Is this a bug?

Update: No, of course, it's not a bug. @ and + being non word chars, there is no \w char to match. Duh. ;--> Thanks for the many quick responses.

In reply to Regex word boundary and escaped characters by ryantate

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.