use warnings;
use strict;

my $text = "I am a GIRL, a Real GIRL. A test WITH Multiple conDITions AND other tests.";

print map{"$_ "}
      map{$_ = lc($_) unless (($_ eq uc $_) and length $_ > 1 ); $_ }
      map{split ' ',$_}$text;
      
__END__
Prints: 
i am a GIRL, a real GIRL. a test WITH multiple conditions AND other tests. 

##</code><code>##

use warnings;
use strict;

my $text = "I am a GIRL, a Real GIRL. A test WITH Multiple conDITions AND other tests.";

print "".onlyAllcaps ($text);


sub onlyAllcaps
{
   my $input = shift;
   
   my @words = split ' ',$text;
   foreach my $word (@words)
   {
      $word = lc($word) unless (($word eq uc $word) and length $word> 1 )
   }

   my $output = join " ",@words,"\n";
   return $output;
}

__END__
Prints:
i am a GIRL, a real GIRL. a test WITH multiple conditions AND other tests.