I tried but failed to quickly find the docs for Pod::Usage version 1.33. If it supports -sections then I'd do something like this:

# get your command arguments and conditionally set $help_command
# from your example: svn help commit
# $help_command should contain 'commit'
if (defined $help_command) {
  pod2usage(-verbose => 99, 
            -sections => [ $help_command ] );
} else {
  pod2usage( ... ); # normal usage of help without $help_command defin
+ed
}
[download]

Don't forget to define a 'commit' section in your POD.