in reply to Edit a New file in place after reading it in

Help us help you with a Short, Self-Contained, Correct Example

Lines 44 - 63 of your sample code would have been sufficient, if I am understanding your question correctly. 

my %substitutions =  ( 'Xi Wong' => 'Lucca P.', 'MG5237ALL5X' => 'MG54
+15DP', 'SI' => 'SA' );

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

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But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us. Romans 5:8 (NASB)

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