#! perl -slw
use strict;
use Time::HiRes qw[ time ];

print STDERR time;
my $s;
do{ local( @ARGV, $/ ) = $ARGV[0]; $s = <>; };
print STDERR time;

$s =~ tr[\t][ ];

print STDERR time;

open O, '>', $ARGV[1] or die $!;
{ local $\; print( O $s ); }
close O;

print STDERR time;

__END__
[ 0:57:20.47] C:\test>984648-3 500MB.csv junk.txt
1343779056.03211
1343779058.22142
1343779058.70098
1343779061.99852

[ 0:57:42.05] C:\test>