@FIELDS=split(/:/, "$RECORD");

You are splitting the text version of your regular expression on the ':' character, and since the regexp has that character in it, the split does the wrong thing.

Perhaps something along the lines of:

my ($TNAME, $TVALU, $TFILE, $REGEX, $REST);
if ($RECORD =~ m/^([^:]+):([^:]+):([^:]+):(.+):([^:]+):$/) {
  $TNAME = $1;
  $TVALU = $2;
  $TFILE = $3;
  $REGEX = $4;
  $REST  = $5;
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Basically, you want to remove everything that is not the regexp (which do not contain ':'), and everything that is left ((.+)) is the regular expression.

Either that, or figure out how to escape the ':' character in the text file. If there are a variable number of fields in the configuration file, then escaping the character might be a better solution.

Changing the number of fields in the configuration file will require alteration of the parsing code. Escaping the ':' character could provide a more resilient solution against added fields.

On a side note, the chomp($REGEX) is useless, since it comes in from the middle of the line.