I originally had this working in only 54 characters, but it seemed too obvious.
It runs both in Linux ("perl <script>") and in Windows (but use a "cmd" shell so you can see the output).
$;='aq';$^X=~m;.+[/\\]([^\.]+);;`$1doc $1f$;4`=~m;"(.u.{22});;print$1,
+$/
If you like the results, don't "peek" at how it's done yet ... try running it with the '4' changed to a '1', and it becomes all lowercase! ...
$;='aq';$^X=~m;.+[/\\]([^\.]+);;`$1doc $1f$;1`=~m;"(.u.{22});;print$1,
+$/
Finally, change the string '
"(.u.{22});' near the end of the line to '
th\.(.{17});m', and I think you'll truly be surprised:
$;='aq';$^X=~m;.+[/\\]([^\.]+);;`$1doc $1f$;1`=~m;th\.(.{17});m;print$
+1,$/
Update: What am I thinking?!! I forgot the most important person of all:
$;='aq';$^X=~m;.+[/\\]([^\.]+);;`$1doc $1f$;1`=~m;y (L.{9});m;print$1,
+$/
Update: ambrus pointed out that he had already created an obfuscation based on this method. Sorry about that, ambrus!