An alternative approach to eliminating everything you don't want from a string is to capture only what you do want: it's often easier to define what you want than what you don't. Consider:

c:\@Work\Perl>perl -wMstrict -le
"use Regexp::Common qw(number);
 ;;
 my $str = 'name=0.5e-7,noodle=123.0e5,niddle=1.2,noddle=9';
 ;;
 my $number = qr{ (?<! \d) $RE{num}{real} (?! \d) }xms;
 ;;
 my @numbers = $str =~ m{ $number }xmsg;
 printf qq{'$_' } for @numbers;
"
'0.5e-7' '123.0e5' '1.2' '9'
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See Regexp::Common.