%hash = (
  # note the single-quotes wrapping the double-quotes...
  # I've defined a character string which is, itself, a valid
  # perl expression... which can be eval'd later
  command1 => ' "command_name -n $var1 -p $var2" '
);

$var1 = 'foo';
$var2 = 'bar';
# this is the "later" I promised above, when we eval
# the character string which contains the perl expression
system (eval $hash{'command1'});