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

print STDERR time;
my $s = read_file( $ARGV[0] );
print STDERR time;
$s =~s/\t/ /g ;
print STDERR time;
write_file( $ARGV[1], $s );
print STDERR time;

__END__

[21:35:14.40] C:\test>984648-1 500MB.csv junk.txt
1343767102.78642
1343767106.4356
1343767106.89558
Terminating on signal SIGINT(2)

##</code><code>##

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

print STDERR time;
my $s = read_file( $ARGV[0], scalar_ref => 1 );
print STDERR time;
$$s =~s/\t/ /g ;
print STDERR time;
write_file( $ARGV[1], $s );
print STDERR time;

__END__
[22:14:07.81] C:\test>984648-2 500MB.csv junk.txt
1343769390.96321
1343769394.24913
1343769394.70982
Terminating on signal SIGINT(2)

##</code><code>##

#! 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>