cryptic perl expression
I find the following statement in a perl (actually PDL) program:
Can someone decode this for me, an apprentice in perl programming?
Sure, I'll explain it from the inside out:
\w - matches a
[...] - matches a single character from within the brackets
[\w] - matches a single character that can be used in a word (kinda redundant here)
+ - matches the previous character,
[\w]+ - matches a group of word characters, many times over. This will find a word.
(...) - grouping. remember this set of characters for later.
([\w]+) - match a word, and remember it for later
$ - end-of-line. match something at the end of a line
([\w]+)$ - match the last word on a line, and remember it for later
\/ - a single slash character '/'. it must be escaped by backslash, because slash is special.
\/([\w]+)$ - match the last word on a line, after a slash '/', and remember the word for later. This is probably grabbing the directory/file name from a path.
/.../ - match syntax
/.../i - i means case-insensitive.
All together now:
/\/([\w]+)$/i; - match the last word on a line and remember it for later; the word must come after a slash. Basically, grab the filename from an absolute path. The case insensitive part is irrelevant, \w will already match both cases.
More details about Perl regex here: http://www.troubleshooters.com/codecorn/littperl/perlreg.htm
And as JRFerguson pointed out, YAPE::Regex::Explain is useful for tokenizing regex, and explaining the pieces.