How to use \W in Regular Expression?

Sachin has asked for the wisdom of the Perl Monks concerning the following question:

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Re: How to use \W in Regular Expression? by almut (Canon) on Dec 30, 2009 at 12:08 UTC
The substitution part of `s///` is not a regular expresssion, so it doesn't make much sense to put `\W+` in there. Just remove it: `$str =~ s/$query\W+/<em>$query<\/em> /ig;` [download]	[reply] [d/l] [select]
Re^2: How to use \W in Regular Expression? by Sachin (Acolyte) on Dec 30, 2009 at 12:14 UTC
So could you tell me how to highlight this word "perl" in above program?	[reply]
Re^3: How to use \W in Regular Expression? by almut (Canon) on Dec 30, 2009 at 12:17 UTC
Not sure what you mean. There's no problem with adding `<em>...</em>` around the word "perl", it's just the `\W+` that's inappropriate in the string to substitute... Think of it this way: What concrete characters (and how many) should be substituted from the class of characters that `\W` stands for?	[reply] [d/l] [select]
Re^4: How to use \W in Regular Expression? by Sachin (Acolyte) on Dec 30, 2009 at 12:31 UTC
Re^5: How to use \W in Regular Expression? by ikegami (Patriarch) on Dec 30, 2009 at 12:37 UTC
Re^5: How to use \W in Regular Expression? by almut (Canon) on Dec 30, 2009 at 12:36 UTC
Re^5: How to use \W in Regular Expression? by AnomalousMonk (Archbishop) on Dec 30, 2009 at 13:10 UTC
Some notes below your chosen depth have not been shown here
Re: How to use \W in Regular Expression? by ikegami (Patriarch) on Dec 30, 2009 at 14:29 UTC
Is your question really about how to prevent `$query="perl";` from matching anything in `"This drink is fraperliscious!"`? `$str =~ s/\b\Q$query\E\b/<em>$query<\/em>/ig;` [download] or `$str =~ s/(?<!\w)\Q$query\E(?!\w)/<em>$query<\/em>/ig;` [download]	[reply] [d/l] [select]
Re: How to use \W in Regular Expression? by gube (Parson) on Dec 30, 2009 at 15:25 UTC
\W means Match non-word character. As almut said its not required for replace what you are trying to do. Just `s/$query/<em>$query</em>/i` would be fine. Perl regex	[reply] [d/l]