my ($h,$m,$s) = ...;
$m = "0$m" if $m < 10;
$s = "0$s" if $s < 10;
my $dur = "$h:$m:$s";

##</code><code>##

my ($h,$m,$s) = ...;
my $dur = sprintf("%d:%02d:%02d", $h,$m,$s);

##</code><code>##

%d    Signed 32/64-bit integer
%2d   ...space padded (on the left) to occupy (at least) 2 columns
%02d  ...zero padded (on the left) to occupy (at least) 2 columns

##</code><code>##

print get_duration('s1');

##</code><code>##

print get_duration($durations{s1});

##</code><code>##

print get_duration(@{ $durations{s1} });