Select Code to Download

my @pids;
{
...
while (<$fids_fh>) {
    print if /^$pids_pat;/;
}

my $pids_pat =
    map qr/$_/,
    join '|',
    #map quotemeta,  # We're only dealing with digits
    @pids;

use Regexp::List qw( );
my $pids_pat = Regexp::List->new()->list2re(@pids);