Try this:

sub test2
{
    my ($var2) = shift;
   
    # Perl can implement the if/else idea very code efficiently.
    
    return ("One")    if ($var2 =~ /^1\./ );
    return ("Two")    if ($var2 =~ /^2\./ );
    return ("Three")  if ($var2 =~ /^3\./ );
    return ("UNKOWN");
}

print test2 ("1.00.000"), "\n";
print test2 ("11.00.000"), "\n";
print test2 ("3.abc"),     "\n";

__END__
prints:
One
UNKOWN
Three
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Update:
Well I think we both know that this is a simple example.
The regex'es aren't complicated. Just to demo the idea.