canonpath in File::Spec seems to do the trick. 

use File::Spec::Functions 'canonpath';

print canonpath('foo/../bar/../baz/');

__END__
baz

[download]

lodin

Update: added examplifying code, but see ikegami's reply below.

In reply to Re: Collapsing paths by lodin
in thread Collapsing paths by rvosa

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