NixOS/nixpkgs — pull request #1275 by tomberek (2013-11-25 00:05:23+00:00)
Title: Perl requirement for ddclient

It looks like only the FreeDNS protocol needs it.
Around line 1217 from ddclient script
```HOST:
1212 foreach my $h (keys %config) {
1213 my $proto;
1214 $proto = $config{$h}{'protocol'};
1215 $proto = opt('protocol') if !defined($proto);
1216
1217 load_sha1_support() if ($proto eq "freedns");
1218
1219 if (!exists($services{$proto})) {
1220 warning("skipping host: %s: unrecognized protocol '%s'", $h, $proto);
1221 delete $config{$h};
```
and the actual requirement:
```
######################################################################
1778 ## load_sha1_support
1779 ######################################################################
1780 sub load_sha1_support {
1781 my $sha1_loaded = eval {require Digest::SHA1};
1782 unless ($sha1_loaded) {
1783 fatal(<<"EOM");
1784 Error loading the Perl module Digest::SHA1 needed for freedns update.
1785 On Debian, the package libdigest-sha1-perl must be installed.
1786 EOM
1787 }
1788 import Digest::SHA1 (qw/sha1_hex/);
1789 }
```