gistfile1.pl

#!/usr/bin/perl -w

die "pass GFF\n"
  unless @ARGV;

while(<>){
  chomp;
  my @x = split/\t/;
  die unless@x==9;
  
  my @y = split(/;/,$x[8]);
  
  pop @y unless length $y[-1];
  
  $y[-1] = 'Note='. $y[-1]
    unless index($y[-1], '=') > 0;

  print
    join("\t", @x[0..7], join(';', @y)), "\n";
}

warn "OK\n";