for my $i (351..354) {
     my $param = "<parameters>
<index>/home/nikol123/indri-5.6/4collections</index>
<query> <type>indri</type> <number>$i</number> <text>British Chunnel impact</text> </query>
<fbDocs>10</fbDocs>
</parameters>";
     my $paramfile = "param$i.txt";
     open my $PARAM, ">", $paramfile  or die "Can't open $paramfile  $!";
     print $PARAM, $param;
     close $PARAM;
     do_something_with($paramfile);
}