It's because you had \b switches to match a word boundary, where # is not considered as a word, but rather a boundary instead.

Update: The following code is flawed, see Abigail-II's comment below.

If you want to match '#' in your regex, you could do this instead -
my $str = "This is a line # with comment";
my $word = '#';
while ($str =~ /[^\B#]($word)[^\B#]/g) {
    print "$1\n";
}
__OUTPUT__
#

[download]
Notice the [^\B#] idiom, what it means is that I want a character set of \B, non-word boundary, and #, and then take the compliment of the set. So the result will be a word boundary that does not match on the # character.

Update: Thanks to Abigail-II for the detailed analysis of [^\B#].

Ok, below is one way I think would fix the problem -
my $str = "This is a line # with comment Boss.";
my $word = "#";

# define custom \b
my $b = qr/(?:(?=\S)(?<!\S)|(?!\S)(?<=\S))/;

# and match on non-space characters
while ($str =~ /$b(\S+)$b/g) {
    print "$1\n";
}

# or ignore the boundaries completely and match on non-space character
+s
while ($str =~ /(\S+)/g) {
    print "$1\n";
}

[download]

In reply to Re: regexp pattern match help? by Roger
in thread regexp pattern match help? by Elijah

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