gistfile1.pl

#!/usr/bin/env perl
#

$ghc = '/usr/bin/ghc'; # where is ghc
@ghc_options  = ();          # e.g. ('-fglasgow-exts')
@ghc_packages = ();          # e.g. ('QuickCheck')

### the following should not been edited ###

use File::Temp qw /tempfile tempdir/;
File::Temp->safe_level( File::Temp::HIGH );

($source, $base_dir) = @ARGV;

@command = ($ghc,
            '-fno-code',
            "-i$base_dir",
            $source);

while(@ghc_options) {
    push(@command, shift @ghc_options);
}

while(@ghc_packages) {
    push(@command, '-package');
    push(@command, shift @ghc_packages);
}

$dir = tempdir( CLEANUP => 1 );
($fh, $filename) = tempfile( DIR => $dir );

system("@command >$filename 2>&1");
open(MESSAGE, $filename); 
while(<MESSAGE>) {
    # this code is wrong - you need a grouping around the .hs|.lhs bit if you
    # want it to properly notice lhs files and point to the right place
    # if(/^\S+\.hs|\.lhs:\d*:\d*:.*/) {
    if(/^\S+(?:\.hs|\.lhs):\d*:\d*:.*/) {
        print "\n";
    	chomp $_;
    	print $_;
    	next;
    }
    if(/\s+(.*)/) {
    	$rest = $1;
        chomp $rest;
    	print $rest;
        print " ";
    	next;
    }
}
close($fh);
print "\n";