$ perl -cw -e '$no_days = "(TO_DAYS(dateadded)-TO_DAYS(Now())>=-$newda
+teadded)";'
Name "main::newdateadded" used only once: possible typo at -e line 1.
Name "main::no_days" used only once: possible typo at -e line 1.
-e syntax OK
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Ergo, valid Perl.