Disclamer: Not tested.

sub getfilefromrc {
    open my $rch, '<', $_[0] or croak("Can't open $_[0]: $!");
    my $fn;
    while (<$rch>) {
        if (/^\s*\$RC\{model_root\}/) {
            if (/'([^']+)'\s*$/) {
                $fn = $1;
                last;
            }
        }
    }
    defined($fn) or croak("Can't find filename in RC file ($_[0])");
    return $fn;
}
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