#!/usr/bin/perl -w

# Strict
use strict;
use warnings;
use Data::Dumper;

# User defined
my $text = "
                                       It's
                                    been said
                                  ever so often
                                by many an expert
                              that in ol' plain text
                                one neer can get a
                                 round tuit, but
                                    just look
                                       here
";

# Main program

$text =~ s/(?<!\s) (?!\s)/@/gms;             # Turn inner spaces into '@'
print "Debug1>  text = [$text]\n";           # Show text
$text =~ s/\s+//;                            # Strip all other spaces
$text =~ s/\n/@/gs;                          # Convert newlines to '@'
my @text = grep { /\S/ms } split //, $text;  # Split text into characters

# Find the mass of the diamond
my $mass = (my $temp = $text) =~ s/\S/./g;
print "Debug2> mass = [$mass]\n";

# Circle mass 'm' = pi * r^2, so the radius 'r' = sqrt(m / pi)
my $radius = sqrt($mass / 3.14159265358);
print "Debug3> radius = $radius\n";

# Format the text into a circle, 
my $circle = "";
my $aspect = 1.0;
for (my $row = -($radius + 10); $row <= ($radius + 10); $row++) {
    for (my $col = -($radius + 10); $col <= ($radius + 10); $col++) {
        my $char = " ";
		if (($aspect * $row) ** 2 + $col ** 2 <= $aspect * ($radius ** 2)) {
			$char = shift @text || '*';
		}
        $circle .= ($char eq '@'? ' ': $char);
    }
    $circle .= "\n";
}

# Show the resulting circle
print "$circle\n";

__END__

Output:
Debug1>  text = [
                                       It's
                                    been@said
                                  ever@so@often
                                by@many@an@expert
                              that@in@ol'@plain@text
                                one@neer@can@get@a
                                 round@tuit,@but
                                    just@look
                                       here
]
Debug2> mass = [120]
Debug3> radius = 6.18038723238067


             It's be
            en said e
           ver so ofte
           n by many a
           n expert tha
           t in ol' pla
           in text one
           neer can get
            a round tu
            it, but ju
             st look
               here