For unixy stuff I use this. It gives me an absolute path without worrying about how trailing slashes were handled.

sub abspath {
    # split anything that looks like a unix path seperator            
+          
    my @tokens = map { defined $_ and split /\/+/ } @_;
    @tokens = grep { $_ ne '' } @tokens;
    return join( '/', '', @tokens );
}
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Which could adapted to use File::Basename which would handle other OS's.