Here is one way I use it:

use strict;
use Data::Dumper;

my %dat;
$dat{a} = sprintf("%5.2f", 3.141);
$dat{b} = sprintf("%20s","hello");
print Dumper %dat;
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That is, I like to store formatted data sometimes. In fact, I have written code like this:

use strict;
use Data::Dumper;
my $format_a = "%5.2f";
my $format_b = "%20s";
my %dat;
$dat{a} = sprintf($format_a, 3.141);
$dat{b} = sprintf($format_b,"hello");
$dat{c} = sprintf($format_a, 12.34567);
print Dumper %dat;

This way formats can easily be controlled in a central place.
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--traveler