Maybe it's worth to include the following, which has bitten me once too: One common use is to get regexp from an external source - for instance, your commandline - into your program, so you end up having somewhere something like:
if($line =~ /$pattern/) { ... }
The trap here is when $pattern happens to be the null string, yielding the Regexp
//. This special regexp, unless it is used as argument to the
split function, means: "Match again the most recently encountered regexps", which can lead to pretty bizarre program behaviour.
--
Ronald Fischer <ynnor@mm.st>