You could use Date::Calc like this:

use strict;
use warnings;

use Date::Calc qw/Date_to_Text Add_Delta_Days Today/;

print "Yesterday: ", 
      Date_to_Text( Add_Delta_Days( Today(), -1 ) ), 
      "\n";
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This approach has the advantage of being very easy to read, and less prone to goofing up the math behind subtracting a day from localtime, and it should avoid daylight savings time issues.