$/ = undef or
$data = <> and
$data =~ s{
    ^TABLE;([^;\n]+).*$
    |
    ^COLUMN;(.+?);.*$
}{$1 ? (($t=$1),"") : "$t.$2"}mexg;

print $data;

##</code><code>##

perl -e '$/=undef or $_=<> and s{^TABLE;([^;\n]+).*$|^COLUMN;(.+?);.*$}{$1?(($t=$1),""):"$t.$2"}mexg and print;' data.txt

##</code><code>##

perl -e'local$/or$_=<>,s{^TABLE;(.+?)$|^COLUMN;(.+?);.*$}{$1?(($t=$1),""):"$t.$2"}mexg and print;' data.txt