#!/usr/local/bin/perl
use strict;

my $data = join( '', <DATA> );

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

print $data;

__DATA__
CREATE TABLE "SO"."EL_HAND_RECEIPT"
(
    EL_ID             NUMBER(20) NOT NULL,
    UIC               VARCHAR2(6) NULL,
    ISSUE_RECEIPT_CD          VARCHAR2(1) NOT NULL,
    PRIMARY KEY (EL_ID)
)
TABLESPACE DATA

##</code><code>##

:!test.pl
CREATE TABLE "SO"."EL_HAND_RECEIPT"
(
    EL_ID             NUMBER(20) NOT NULL,
    UIC               VARCHAR2(6) NULL,
    ISSUE_RECEIPT_CD          VARCHAR2(1) NOT NULL,
    CONSTRAINT PK_EL_HAND_RECEIPT PRIMARY KEY (EL_ID)
)
TABLESPACE DATA