#!/usr/bin/perl

use strict;
use DBI;

my $tablename = 'table_name';  # maybe this is really a file name?
my $last_col = 20; # pick a number (any number?) -- you must know the right one

my $colnames = join( ',', map { sprintf( "field%d", $_ ) } 1 .. $last_col );
my $placehld = join( ',', map { '?' } 1 .. $last_col );

my $sql = "insert into $tablename ($colnames) values ($placehld)";

print STDERR "Ready to do:\n $sql\n";  # see how that looks

open( DATAFILE, "wheres_the_data" ) or die "wheres_the_data: $!";

my $dbh = DBI->new( blah blah );
my $insert_data = $dbh->prepare( $sql );

foreach (<DATAFILE>)
{
    chomp;
    my (@ROW) = split /,/;
    if ( @ROW != $last_col ) {
        # what do you do if the number of "fields" in ROW
        # is greater than or less than the number of columns
        # in the table?  Think about that, and do it here.
    } else {
        $insert_data->execute( @ROW );
    }
}