my $regexp = "(?:ftp:\/\/)?\/{5}(a-z_)\/";
my $link = "ftp://ftp.ensemblgenomes.org/pub/release-36/metazoa/vcf/ixodes_scapularis/ixodes_scapularis_incl_consequences.vcf.gz";

if ($link =~ /$regexp/) {
    print "Captured info: $1 \n";
}