I think the other important point to make is that the order of the sub-patterns in the ordered alternation is critical: 

c:\@Work\Perl\monks>perl -wMstrict -le
"my $ufp = qr{ \d* [.]? \d+ | \d+ [.]? \d* }xms;
 ;;
 for my $s (qw(0.12  .34  56.  78)) {
   printf qq{'$s' -> };
   printf qq{'$1' \n} if $s =~ m{ ($ufp) }xms;
   }
 ;;
 my $s = '0.12 -0.98 .34 -.76 56. -54. 78 -32 bla bla abc.def42 .7zx';
 printf qq{'$1' } while $s =~ m{ ($ufp) }xmsg;
"
'0.12' -> '0.12'
'.34' -> '.34'
'56.' -> '56'
'78' -> '78'
'0.12' '0.98' '.34' '.76' '56' '54' '78' '32' '42' '.7'

[download]
(See  '56.' and  '-54.' instances.)

Give a man a fish:  <%-{-{-{-<

In reply to Re^3: regex to capture an unsigned decimal value, but also preserve the user's formatting. by AnomalousMonk
in thread regex to capture an unsigned decimal value, but also preserving the user's formatting. by darisler

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