This is a variation on stevieb's reply. The optional  ftp:// doesn't make much sense unless it's anchored to something; I anchor it with  \A absolute-start-of-string. (Update: By the same token, the  (?: [^/]+ /){5} five-level-deep directory nesting pattern only makes sense if you specify five levels deep from what. Again,  \A is used, but I don't know if this is appropriate to stefanches7 true requirement.)

c:\@Work\Perl\monks>perl -wMstrict -le
"my $regexp = qr{ \A (?: ftp://)? (?: [^/]+ /){5} ([a-z_]+) / }xms;
 ;;
 my $link =
   'ftp://ftp.ensemblgenomes.org/pub/release-36/metazoa/vcf/ixodes_sca
+pularis/ixodes_lapuscaris_incl_consequences.vcf.gz';
 ;;
 print qq{captured '$1'} if $link =~ $regexp;
"
captured 'ixodes_scapularis'
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