RT#42122 - untaint $content before using it in 'truncate'

[fipp]

See my post in https://rt.cpan.org/Ticket/Display.html?id=42122, posted Thu Jan 15 11:00:14 2015.

Using perl scripts in taint mode served by an Apache web servers produces warnings when the variable $content is read from:

Insecure dependency in truncate while running with -T switch at /tmp/locktest/File/NFSLock.pm line 417, <$fh> line 2.
\t(in cleanup) Insecure dependency in truncate while running with -T switch at /tmp/locktest/File/NFSLock.pm line 417, <$fh> line 2.

The merge request untaints $content before using it in 'truncate'.