First, a note: the join operator is already reading the whole file into memory (the <FILE> is evaluated in list context, so it returns all the lines from the file), so there is no need for the while loop. You should just say:

#!/usr/bin/perl -w
use strict;

my $file = "go.txt";

print "\nOpening $file\n";

open(FILE, "< $file") || die "OLD FILE ERROR: Unable to open file: $!\
+n";
open(OUT, "> $file.new") || die"NEW FILE ERROR: Unable to create new f
+ile: $!\n";

my $data=join('',<FILE>);
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Anyway, there is an error in the regexp, and one in the modifiers. The line should be:

$data =~ s/(CREATE TABLE "SO"\.")([^"]+)(.+?)(PRIMARY KEY)/$1$2$3CONSTRAINT PK_$2 $4/msg;

I changed two things:

• I changed from (.+) to (.+?), so that it matches the shortest string. Otherwise, when there are more than one "CREATE TABLE" in the file, it would match the first "CREATE" with the last "PRIMARY KEY".
• I added the g modifier, so that every match will be changed.

And, of course, then you have to print the result:

print OUT $data;

print "Closing $file\n";

close(OUT) || die "Unable to close OUT file: $!\n";
close(FILE) || die "Unable to close OLD file: $!\n";
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