in reply to regexp help needed

I recommend Regexp::Common.

use Regexp::Common qw(number);

$_ = '#total mean for 530.2 nm = 411.67 W/m**2, dev= 0.2%';

if (/$RE{num}{real}{-keep}/) {
  print "$1\n";
}

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<http://dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

In Section Seekers of Perl Wisdom