c:\@Work\Perl\monks>perl -wMstrict -le
"use Regexp::Common;
 ;;
 my @records = (
   'BCInletTemperature = 90[C]',
   'BCInletTemperature = 33.56[C]',
   'Whatever   =   -.012[C]',
   'Wrong = 90 [C]',
   'AlsoWrong = 9.0.1[C]',
   );
 ;;
 for my $record (@records) {
   printf qq{'$record' -> };
   my $got_temp =
   my ($temp) = $record =~ m{ = \s+ ($RE{num}{real}) \[ }xms;
   if ($got_temp) {
     print qq{temp '$temp'};
     }
   else {
     print 'no got temp';
     }
   }
"
'BCInletTemperature = 90[C]' -> temp '90'
'BCInletTemperature = 33.56[C]' -> temp '33.56'
'Whatever   =   -.012[C]' -> temp '-.012'
'Wrong = 90 [C]' -> no got temp
'AlsoWrong = 9.0.1[C]' -> no got temp