Maybe hash operations are slow, so let's do away with them :)

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11152065
use warnings;

{
my @r2d;
@r2d[qw(1 12 2 13 3 34 4 35 5 56 6 57 7)] =
  qw(1 4 5 9 10 40 50 90 100 400 500 900 1000);
use List::Util qw( sum );
sub roman_to_dec3
  {
  sum @r2d[ shift =~ tr/ivxlcdmIVXLCDM/1-71-7/r =~ /5?[67]|3?[45]|1?[2
+3]|1/g ]
  }
}

my @testdata = ( qw( XLII LXIX mi cd xcix mdclxvi cdxliv
  i ii iii iv v vi vii viii ix x xi xii xiii xiv xv) );
for my $r (@testdata) {
  print "$r: ", roman_to_dec3($r), "\n";
}
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