Step 1

mkdir ~/perl

Step 2

perl -MCPAN -e 'install SVN::Notify'

This command will try to do something, then most probably fail. That's OK.

Step 3

Change ~/.cpan/CPAN/MyConfig.pm to contain:
'makepl_arg' => q[PREFIX=/home/username/perl LIB=/home/username/perl/lib],
'mbuildpl_arg' => q[install_base=/home/username/perl],

Step 4

perl -MCPAN -e 'install SVN::Notify'

This should now install properly

Step 5

Running

~/perl/bin/svnnotify

should produce:

Missing required "--repos-path" parameter

Step 6

cd ~/svn/REPO/hooks
vim post-commit

Paste this

#!/bin/sh
 
REPOS="$1"
REV="$2"
PATH=/usr/bin:/bin:~/perl/bin
PROJECT=CHANGEME
export PERL5LIB="$HOME/perl/lib/perl5:$PERL5LIB"
 
svnnotify --repos-path "$REPOS" \
          --revision "$REV" \
          --svnlook /usr/bin/svnlook \
          --to CHANGEME \
          --from $COMMITTER@$PROJECT.com \
          --with-diff --subject-cx --handler HTML::ColorDiff \
          --max-diff-length 15000 --subject-prefix commit-

The last line

--max-diff-length 15000 --subject-prefix commit-

is optional.
Save and exit.

Step 7

chmod a+x post-commit

You're done!