You open the script itself (location stored in $0) on filehandle F and assign the first two lines to $_.

Then you start a substitution operating on $_, with ; as a delimiter, so de-obfuscated (using a | as delimiter) it looks like:

$_=~s|^.*?\/(..).*?i(.).(.*?)\s.*?\ss(.)(.).(.).*|J$1$4 a$2o$4he$5 $3 
+ha$6ke$5!|;
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You basically scan the first two lines for some stuff:

1. The two chars following the first slash go into $1 ('us')

   #!/usr/bin/perl -w
   use strict;
   

2. Then you scan for the next 'i' and save the following char in $2 ('n')

   #!/usr/bin/perl -w
   use strict;
   

3. You skip the next char and save everything up to the next space in $3 ('perl')

   #!/usr/bin/perl -w
   use strict;
   

4. You skip to the next space followed by 's' and save the next char in $4 ('t')

   #!/usr/bin/perl -w
   use strict;
   

5. The next char goes into $5 ('r')

   #!/usr/bin/perl -w
   use strict;
   

6. Then skip one and save the last in $6 ('c')

   #!/usr/bin/perl -w
   use strict;
   

and then print the new value of $_.

But I still don't know what the c in cjaph stands for ...