Select Code to Download

sub build_regexp {
  my $expr = join '|', map { "(?:To|is)\:\S+\@$_" } @_;
...
  $expr;
}

my $writeFh = new FileHandle ">> myout.log";
my $is_subset = build_regexp(@allSubSets);
...
    next unless /$is_subset/;
    print $writeFh <$fh>;   
}