check and see with wxperl_usage / wxperl-usage / wxPerl::Usage / Class Method Browser , available methods, method invocation syntax, link to docs

Also, you didn't notice that "convenience method" on the wxwidgets website

http://docs.wxwidgets.org/trunk/search.php?query=AddMany

Perl doesn't really need such a convenience method

$sizer->Add( $_, 1, Wx::wxEXPAND() ) for $code, $text, $tree, $snickerdoodle;

But you could make one

sub Wx::Sizer::AddMany { my $sizer = shift; $sizer->Add($_) for @_; }
sub Wx::Sizer::AddMany { my ( $self, @many ) = @_; $self->Add($_) for 
+@many; }

sub Wx::Sizer::AddMany {
    my ( $self, $flags, @many ) = @_;
    if ( 'ARRAY' eq ref $flags ) { $self->Add( $_, @$flags ) for @many
+; }
    else                         { $self->Add($_) for $flags, @many; }
}
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