To rephrase your problem in a way that may make the answer more obvious, you need to:

1. Edit the file in-place
2. Keep track of the most recent CREATE TABLE line
3. Extract the table name out of it if it exists, and use it to keep up-to-date what table we're in
4. Otherwise, replace every occurrance of the string "PRIMARY KEY" with the string "CONTRAINT PK_(table name) PRIMARY KEY"

Armed with this knowledge, we can go about writing something that does this. I don't know enough about your problem to do #3 above reliably, so you'll probably have to change that regex in the following code:

#!/usr/bin/perl -pi
# The -p wraps the following code in a loop for each line,
# and the -i tells perl we're editing the file in-place.
# Give this program the filename(s) to change as arguments
# on the command line.

# Extract and update the table name if this is a CREATE TABLE line
$table = $1 if (/CREATE TABLE "SO"."([^"]+)"/);

# Change the "PRIMARY KEY" bit if we find it.
s/(PRIMARY KEY)/CONTRAINT PK_$table $1/;
[download]

I hope that makes some amount of sense.

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'