$P2=qr'\s*<P2>\s*'xgi;
$AmendmentPrefix= qr'BlockAmendment\ [^>]+ >'xgi;
$AmendmentSuffix= qr'</P2></Block\ Amendment>'xgi;

$bBlkTx =~ s{ $AmendmentPrefix $P2  (.*?)  $AmendmentSuffix }
            { \n<lq><P2>   $1   <\/P2>\n<\/lq> }xgi;