Thanks for the tip. I found slightly more understandable code in File::Spec which has resulted in the following regexps: for Unix... 

qr{(\A (?: .* / (?: \.\.?\z )? )? [^/]* )}msx;

[download]
...and Windows (includes UNC paths)... 
qr{(\A
    (?:
        [a-zA-Z]:
        |
        (?:\\\\\\\\|//)[^\\\\/]+[\\\\/][^\\\\/]+
    )?
    (?:.*[\\/](?:\.\.?\Z(?!\n))?)?
    .*
)}msx;

[download]

--
જલધર

In reply to Re^2: One true regexp for untainting windows filenames? by jaldhar
in thread One true regexp for untainting windows filenames? by jaldhar

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