use Modern::Perl;

my $filename = $ARGV[0];

die "Usage: modulenamechanger.pl filename newmodulename oldmodulename\
+n"
  unless @ARGV == 3;

open my $INFILE, "<", $filename or die "Failed to read file $filename 
+: $!";
say "Now parsing $filename";
my @file = <$INFILE>;
close $INFILE;

open my $OUTFILE, '>', $filename or die "Failed to create $filename";

my $match = qr "module\s*($ARGV[2])";
say "Matching: $match";

for my $line (@file) {
    if ( $line =~ m(^//) ) {
        print $OUTFILE $line;
        next;
    }
    $line =~ s/$match/module $ARGV[1]/;
    print $OUTFILE $line;
}