foreach my $line (<$infh>) {
    if ($line =~ /$re_data/) {
        # Split on whitespace, surround with parens, join with commas
        push @data, "(" . join(",", split(/\s+/, $line)) . ")";
    }
}

##</code><code>##

# Simply 'join' all data; last record contains neither comma nor newline.
my $data = join(",\n", @data);

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use feature qw( say );
use IO::File;


##################
## User-defined ##
##################
my $input   = 'in.txt';       # Input file
my $output  = 'out.txt';      # Output file
my $re_data = qr/^[0-9]+/;    # Detect lines containing records

##################
## Main program ##
##################
# Read the input
my $infh = IO::File->new($input) or die "Can't read '$input' ($!)";
my @data = ( );

foreach my $line (<$infh>) {
    if ($line =~ /$re_data/) {
        # Split on whitespace, surround with parens, join with commas
        push @data, "(" . join(",", split(/\s+/, $line)) . ")";
    }
}
close($infh);

# Simply 'join' all data; last record contains neither comma nor newline.
my $data = join(",\n", @data);

# Create the output
my $text = qq{
    SELECT CUSTOMERID, ORDERID, CUSTOMERNAME, CUSTOMERLOCATION
    FROM DB.CUSTOMER_DATA
    WHERE (CUSTOMERID, ORDERID, CUSTOMERNAME, CUSTOMERLOCATION) IN (
      $data
    )
};
$text =~ s/\n\s+/\n/g;    # Remove indentation (for "looks")

# Write the output
my $outfh = IO::File->new;
open($outfh, '>', $output) or die "Can't write '$output' ($!)";
print $outfh $text;
close($outfh);
say "Wrote '$output'";

##</code><code>##

SELECT CUSTOMERID, ORDERID, CUSTOMERNAME, CUSTOMERLOCATION
FROM DB.CUSTOMER_DATA
WHERE (CUSTOMERID, ORDERID, CUSTOMERNAME, CUSTOMERLOCATION) IN (
(0001,20000001,john,CA),
(0002,30000002,neill,WI),
(0003,40000003,joe,GA),
(0004,50000004,will,IL),
(0005,60000005,mike,IN),
(0006,70000006,bill,AK)
)