If you know the location of the config file relative to the script which uses your module, you can use FindBin:

# Parent script resides in /usr/local/myproject/bin
# Module and config file reside in /usr/local/myproject/lib
use FindBin qw($Bin);
sub get_config
{
    my $CONFIGPATH = "$Bin/../lib/acme.config";
    open (CONFIG, "<$CONFIGPATH") or die "$0: File '$CONFIGPATH': $!";
    undef $/;
    my $c=<CONFIG>;
    close CONFIG;

    return $c;
}
[download]

A couple of other notes: <list>

You should get in the habit of explicitly directing your open() calls. E.g. use "<$CONFIGFILE" instead of "$CONFIGFILE". In this particular case it isn't a big deal, but if $CONFIGFILE was supplied by a user, that user could set it to something bad like "|rm -rf /*".

chomp() operates directly on the variable you give it as an argument, so returning chomp($c) won't do what you think it does.

chomp() doesn't do anything at all in slurp mode ($/ = undef) anyway. :)

</list>

-Matt