The regex is not recognizing the sprintf as a function in the second part of the s/// operator, so it's probably better (and more legit) to break this into two lines:

if ($url_text =~ m/([^;\/?:@&=+\$,A-Za-z0-9\-_.!~*'()])/ )
{
  $url_sub = sprintf( "%%%02X", ord( $1 ) );
  $url_text =~ s/([^;\/?:@&=+\$,A-Za-z0-9\-_.!~*'()])/$url_sub/;
}
[download]

Update Or , duh, use the s///e modifier (stupid me...)

$url_text =~ s/([^;\/?:@&=+\$,A-Za-z0-9\-_.!~*'()])/sprintf( "%%%02X",
+ ord( $1 ) )/ge;
[download]

What I have above won't catch multiple URLs on the same line.

---

Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain