actually It tried it this way (line4):

my $file='T:\temp\temp.txt';
[download]

and this way:

my $file="T:\\temp\\temp.txt";
[download]

(with the double quote the initial backslash has to be escaped lest a \t tab be interpreted)
anyway.... both brought down the same error. also tried

tie my @lines, 'Tie::File', $file or die 'tie failed';
[download]

...and...

tie my @lines, 'Tie::File', "$file" or die 'tie failed';
[download]

to no avail..... (same error)