Two things stand out to me. First, the script error is being produced because of missing semicolons after the add statements. In Perl, semicolons are required at the end of most lines of code.
In addition, "Q1_2" is valid only when using a checkbox select question. For a non-checkbox select question, you want to see if "Q1" equals 2.
Begin Unverified Perl
if (GETVALUE("Q1") == 2)