This solution takes as its first argument the number of ways to split a file, and the remainder of arguments are taken to be files which need to be split. It does not delete the originals.

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

my $parts = shift; ### how many parts to split
my @file = @ARGV;  ### the files to split

foreach ( @file ) {

  ### how big should the new file be?
  my $size = -s $_;
  my $buf_size = $size / $parts;

  ### ready a buffer for the data
  my $buf = '';

  ### open the input file
  open ( In, $_ ) || warn "Cannot read $_: $!\n";
  binmode ( In );

  ### for as many parts as there are, read
  ### the amount of data, then write it to
  ### the appropriate output file.
  for ( my $i = 0; $i < $parts; $i++ ) {

    ### read an output file worth of data
    read ( In, $buf, $buf_size ) || warn "Read zero bytes from $_!\n";

    ### write the output file
    open ( Out, "> $_$i" ) || warn "Cannot write to $_$i: $!\n";
    print Out $buf;
    close ( Out );

  }

  ### we're done spliting the input file
  close ( In );
}
exit;
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Its weakness is it only loads one buffer per output segment, and for greater usability it should probably loop if it's a huge size. I don't see this being a huge problem given the nature of the program, though, because there's some place the split files are going that's too small for the original file, so the parts should be small enough for main memory. I'll therefore leave more exotic buffer manipulation as an exercise.

Chris
_Boo!

Originally posted as a Categorized Answer.