#!/usr/bin/perl

use strict;
use warnings;

undef $/;

my $file = shift;
my $module = shift;
my $replace = shift;

open ( my $fh, "<", $file);
my $data = <$fh>;
close $fh;
print $data;

print qq(\n\n\n);

if ( $data =~ m/module $module/ ) {
    $data =~ s/$module/$replace/;
}

# ... # $data =~ s/$module/$replace/;

print $data;

__END__

Karls-Mac-mini:monks karl$ ./new.pl test.txt  OLD "What are you doing?"
 //Verilog HDL for "tt", "hh" "functional"
// if i write the word module here the script goofs up
`timescale 1ps/10fs


module OLD(Y, A, B );
    output Y;
    input A;
    input B;

endmodule



 //Verilog HDL for "tt", "hh" "functional"
// if i write the word module here the script goofs up
`timescale 1ps/10fs


module What are you doing?(Y, A, B );
output Y;
input A;
input B;

endmodule