Two-column code (like two-column research papers ;-) )

split-2col.pl

#!/usr/bin/perl -w

$blk = 0;
while (<STDIN>) {
    chomp $_;
    if (m/\s>\|<\s/) {
        ($l, $r) = split (/\s>\|<\s/);
        print "$l\n";
        $rhalf{$blk} = { 'start'=>$., 'code' => '' } if not defined $rhalf{$blk};
        $rhalf{$blk}{'code'} .= "$r\n";
    } else {
        print $_, "\n";
        $blk++;
    }
}
foreach $k (keys %rhalf) {
    print "#line ",$rhalf{$k}{'start'},"\n";
    print $rhalf{$k}{'code'};
}

__DATA__
// $ cat thefoll.c | above.pl > tmp.c && gcc tmp.c
#include <stdio.h>

int main (int argc, char *argv[])     >|<  int func(int x)       
{                                     >|<  {                    
    int x = 99;                       >|<      if (x) return x;
    printf("\n TEST: %d\n", func(x));  >|<      return -1;     
    return 0;                         >|<  }                 
}                                     >|<