sub test1
{
        my $arg1    = shift;
        # but if you wanna print $arg2 then use '' instead of undef otherwise you get warning
        # and you do have use strict; use warnings; at the top right? :)
        my $arg2    = @_ >= 2 || ref $_[0] ne 'ARRAY' ? shift : undef;
        my $argrest = shift;

        print "arg1=$arg1, arg2=$arg2, argrest=@$argrest\n\n";
}

test1('arg1', [qw/foo bar/]);
test1('arg1', \@otherargs);
test1('arg1', 'arg2');
test1('arg1', 'arg2', [qw/foo bar/]);