Key  Value

PR1  2
PR2  4
PR3  1
PR4  3

##</code><code>##

$input = &process1 ($input)
$input = &process2 ($input)
$input = &process3 ($input)
$input = &process4 ($input)

##</code><code>##

The way i tried one way (here i have changed subroutine name as per the key in the hash, which i don't want):

for (sort keys %po)
{
 
	$input = &$_ ($input); 
}

##</code><code>##

The second way i tried but not correct (just i gave a try):

for (keys %po)
{
 
	$input = &process1 ($input) if (po{$_} == 1); 
	$input = &process2 ($input) if (po{$_} == 2); 
	$input = &process3 ($input) if (po{$_} == 3); 
	$input = &process4 ($input) if (po{$_} == 4); 


}