Having a mental map that considers strings numbers and numbers strings allows one to make subtle errors in their programs.

In fact, sprintf returns a string after doing an arithmatic operation. Compare a 2 deciaml point operation via sprintf:

my $num = 4.62899;
$round = sprintf "%.2f", $num;
print "$round\n";
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prints 4.63, which is not a trimming of the string to two decimal places.

For another example consider this snip and output.

my $string = "0.0";
print "string $string is ", ($string ? "True" : "False"), "\n";
print "string $string is ", ($string+0 ? "True" : "False"), "\n";
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Which prints:
string 0.0 is True
string 0.0 is False