How can I get the whoami into a query using DBI

[jim hufford]

use DBI;
my $dbh = DBI->connect('DBI:Oracle:', $ENV{'SCPDB'})
or die "Couldn't connect to database: " . DBI->errstr;
my $sql= qq(delete FROM <table_name> WHERE user_id = '$user');
my $sth = $dbh->prepare($sql) or
die "Couldn't prepare statement: " . $dbh->errstr;
$sth->execute();
$dbh->disconnect;

I need to get the correct unix user sign on in the field so I can remove the entries when the user quits out of the application. I took out the table name in this example.