c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = qq{aaa       : AAA\n}
       . qq{bbb       : BBB\n}
       . qq{ccc       : CCC\n}
       ;
 print qq{[[$s]]};
 ;;
 my $m = qr{ bbb }xms;
 ;;
 my $t = $s =~ s{ .* ^ $m [ ]* : [ ] ([^\n]*) $ .* }{$1}xmsr;
 ;;
 print qq{[[$t]]};
"
[[aaa       : AAA
bbb       : BBB
ccc       : CCC
]]
[[BBB]]