Matching strings with non-word characters

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

I'm trying to match strings such as "X \ n a x" which appear in spam email so I can filter. I can do this but not in a completely satisfactory way. I guess I've just gotten myself confused, but I don't understand why

$_="X ";
if(m'X\ '){print "OK1\n";}
$_='X\ ';
if(m'X\ '){print "OK2\n";}
[download]

produces "OK1" only. I would expect the first match to fail and the second to succeed. Thanks for any comments!

Comment on Matching strings with non-word characters Download Code

Replies are listed 'Best First'.
Re: Matching strings with non-word characters by Tanktalus (Canon) on Apr 17, 2006 at 13:19 UTC
That's because \ is a special character. Thus, you need to escape it if you want it to appear literally. To escape it, just use a backslash - thus, you get `m'X\\ '`. Although I think the single-quote as a seperator is a bit wierd.	[reply] [d/l]
Re^2: Matching strings with non-word characters by chas (Priest) on Apr 17, 2006 at 13:45 UTC
Thanks! I used single quote as separator because I thought that would make the "\" not considered special. I guess that is wrong. (Using single quote prevents interpolation in patterns, though.)	[reply]