...
sub sqlAddress2sqlStatement {
    my $sql_address_string = shift;
    ...
    # do so magic the perlmonks told me about
    ...
    return $sql_statement;
}

my $sql = "select sql_address, osuser from v\$session where user = ?";
...
while( row = $sth->fetchrow_array ) {
      my $thesql = sub sqlAddress2sqlStatement ( $row[0] );
      print "$user is executing $thesql\n";
}