Conversely, you could use \B to match a non-boundary. This would still take into account the beginning of the string, while also allowing for spaces within the string.

$agent = 'PerlBeginnerPerl AndAnother';
$agent =~ s/\B([A-Z])/ $1/g;

# Produces 'Perl Beginner Perl And Another'

$agent = 'PerlBeginnerPerl AndAnother';
$agent =~ s/\B([A-Z])/ $1/g;

# Produces 'Perl Beginner Perl  And Another'
[download]

I realize that spaces within the string is probably outside the scope of the original question, but \B covers his bases and might be a little easier for a beginner to grok than a look-ahead.

-- grummerX