here's a Date::Calc solution -- assumes "business day" is just M-F, so adding 10 just needs to add in the two weekends as well, so is simply:

use Date::Calc qw/Add_Delta_Days/;
my @start = ( $year, $month, $day );
my @end = Add_Delta_Days( @start, 14 );
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If you want to take into account holidays, see the "10) How can I calculate the last business day (payday!) of a month?" example in the Date::Calc docs for reference.