Here we go jepri, I love golf =).. fore!

my $num = 12.3456789;
$num = substr($num, 0, index($num, '.') + 3);

print $num;  #prints 12.34
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Also, here's another that is probably overkill:

use Math::Currency;
my $num = 12.3456789;
$num = Math::Currency->new($num);
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This handles the rounding up/down of the number, where the preceding golf attempt does not. The original post did not ask for rounding, though.