Thank you very much for the replies, specially to halfcountplus for educate me and to Corion for point me (first) to the right trace

I had tried File::MMagic but without success, it seems that is deprecated and some buggy. This is what you can read about the module in cpan:

"The currently recommended module in this area seems to be File::LibMagic. Other alternatives include File::Type (gives less useful results)...

Thus following the trace I finish to arrive to the same module recommmended by Zwon, (thanks also) that works like a charm

# apt-get install libfile-libmagic-perl 
# (run this first once if you are in Debian)

use File::LibMagic ':easy';

my $infile = $ARGV[0]
          print MagicFile($infile),"\n";
          print `file $infile`;
[download]

Last two lines show basically the same info when we provide a filename as first argument.

Problem solved thus. Thanks again