You can write scripts that do it both ways. Just check for @ARGV, if they exist, go on with the script. If they are not there, prompt the user for values.

Installing Perl from source is a good example of this. A minimal example is:

#!/usr/bin/perl
use warnings;
use strict;

my $count = 0;

if( $ARGV[0] ){
   $count = $ARGV[0];
}else{
   print "Enter integer to count to, and press return\n";
   $count = <>;
   chomp $count;
}

for(0..$count){
  print "$_\n";
}
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