To build type:

  perl Makefile.PL
  make
  make install

MapScript requires Swig version 1.3+. If you must re-SWIG things use a command like:

  swig -perl5 -shadow -outdir . -o mapscript_wrap.c ../mapscript.i

and then follow the sequence of steps to install mapscript. 

If you need to change the name of the mapscript module (default=mapscript) you need to:

  1) edit ../mapscript.i and change the name of the swig module
  2) edit Makefile.PL and edit the name 'mapscript' in the WriteMakefile subroutine call

and now build as normal.