I would suggest something like this:

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my @numbers;
foreach my $number (1..3)
{
   my $num = prompt_4_number("Enter number $number of 3");
   push @numbers, $num;
}
print Dumper \@numbers;

sub prompt_4_number
{
   my $prompt = shift; 
   my $number;

   while ( (print "$prompt: "), $number = <STDIN> ) 
   {
      next if $number =~ /^\s*$/;   # re-prompt on blank lines
      $number =~ s/^\s*//;          # delete leading spaces
      $number =~ s/\s*$//;          # delete trailing spaces
      
      if ( $number !~ /^\s*((-?\d*)(\.\d*)?)\s*$/) # not a valid 
                                                   # floating point 
                                                   # number
      {
          print "  Not a valid decimal number!\n";
          next;    # causes a re-prompt
      }
      
      return $number; 
   }
}
  
__END__
C:\TEMP>perl get_nums.pl
Enter number 1 of 3: afd
  Not a valid decimal number!
Enter number 1 of 3: 3.4
Enter number 2 of 3: .5.7.8
  Not a valid decimal number!
Enter number 2 of 3: 5.7
Enter number 3 of 3: 5Avsx
  Not a valid decimal number!
Enter number 3 of 3: 10
$VAR1 = [
          '3.4',
          '5.7',
          '10'
        ];
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