Why doesn't this perl regex capture the last character?

let $PWD = /Unix_Volume/Users/a开发者_JS百科/b/c/d

I would expect:

echo $PWD | perl -ne 'if( /(\w+)[^\/]/ ){ print $1; }'

to display "Unix_Volume". However, it displays "Unix_Volum." Why doesn't the regex capture the last character?

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(\w+) => Unix_Volum

[^\/] => e (not a /)

/ => /

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Try:

export PWD=/Unix_Volume/Users/a/b/c/d
perl -MFile::Spec -e'print((File::Spec->splitdir($ENV{_pwd}))[1],"\n")'

You should always use the modules that come with Perl where possible. For a list of them, see perldoc perlmodlib.

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Since \w doesen't have a forward slash in its class, why do you need [^\/] ?

/(\w+)/ will do. It captures the first occurance of this class.

edit: /.*\b(\w+)/ to capture the last occurance.

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The (\w+)group matches and captures the word characters "Unix_Volume" greedily, leaving the position at the / after "Unix_Volume".

The [^\/] class forces the engine to back up (the greedy + quantifier gives up characters it's matched to satisfy atoms that follow it) to match a character that is not "/", matching the "e" at the end of "Unix_Volume". Since the matched "e" is outside the capturing group you're left with "Unix_Volum" in $1.