my %substitutions =  ( 'Xi Wong' => 'Lucca P.', 'MG5237ALL5X' => 'MG5415DP', 'SI' => 'SA' );

while (my $line = <$base_fh>) {
  foreach my $was (keys %substitutions) {
    $line =~ s/$was/$substitutions{$was}/g;
  }
  print $New_fh $line;
}