What Corion said, that's not a question it's a spec.

• use strict;
• use warnings;
• open files
• check each line of source file
  • If it matches set a found_it flag to 10
  • if found_it is set
    • print line to output file
    • decrement found_it
• That's it

Have a go at coding up the above in Perl.
When it doesn't work and the error messages don't point you in the right direction
      use diagnostics;
If that fails ask a question with some evidence of effort on your part.