#!/usr/bin/perl -w

BEGIN {undef $/;}


# I TRIED 1ST my $match = "^module.*?$ARGV[2].*?([\\(;])"; 2ND my $mat
+ch = "\^module.*?$ARGV[2].*?([\\(;])"; 3RD my $match = "\\^module.*?$
+ARGV[2].*?([\\(;])"

#"(?<=module )$ARGV[2]"
my $match = "(?<=module )$ARGV[2].*?([\\(;])";
#print "$match";

my $filename = $ARGV[0];

open (INFILE, "<", $filename)  or  die "Failed to read file $filename 
+: $! \n";

$string =  <INFILE>;
close INFILE;



#I TRIED "$string =~ s/^$match/module $ARGV[1]$1/sg;";

$string =~ s/$match/$ARGV[1]$1/sg;
#print "$1";


open OUTFILE, ">$ARGV[0]" || die "Failed to create $ARGV[0]\n";
print OUTFILE ($string);
close OUTFILE;
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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;
}
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#!/usr/bin/perl -w

BEGIN {undef $/;}

#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 
+: $!";
print "Now parsing $filename\n";
my @file = <$INFILE>;
close $INFILE;

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

# WITHOUT ABANSAL CONCEPT my $match = qr "module\s*($ARGV[2])";
my $match = "(?<=module )$ARGV[2].*?([\\(;])";

print "Matching: $match\n";

for my $line (@file) {
    print "READING LINE $line \n";
    if ( $line =~ m(^//) ) {
        print "INSIDE IF\n";
        print $OUTFILE $line;
        next;
    }
    else 
    {

print "INSIDE ELSE \n BEFORE change:\t $line\n";
    $line =~ s/$match/moduleXXX $ARGV[1]/;
print "AFTER :\t $line\n";
    print $OUTFILE $line;
    next; 
    }
}
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my.pl f7 NEW OLD
Now parsing f7
Matching: (?<=module )OLD.*?([\(;])
READING LINE //Verilog HDL for "tt", "hh" "functional"
// if i write the word module OLD(Y, A, B ); here the script goofs up
`timescale 1ps/10fs


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

endmodule

INSIDE IF
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OK, let's address this item by item.
1. Modern::Perl: you can replace this by use strict; use warnings; and replace say by print + "\n".
2. What version of Perl are you using?
3. You can use any regex that works (but see point 5).
4. My code does not need an else part.
5. Of course it does not work, the regex you use is wrong. Use the following regex: my $match = qr "module\s*($ARGV[2])\b";. That one works, trust me. It is similar to my previous once, but will reject modulenames that are not exactly the same, but only start with the string you want to replace. It will accept "OLD" but will reject strings like "OLDER", "OLDENBERG", "OLDUVAI",...

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

My blog: Imperial Deltronics

BEGIN {undef $/;}

...

print "Now parsing $filename\n";
my @file = <$INFILE>;
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If you are reading line by line or into an array like this then you need to get rid of the undef $/ since that will make it read the whole file into the first element of the array.