Looks good...

Only thing I can't do now is redirect STDERR to the $tee filehandle... Not sure if I've misinterpreted the IO::Tee instructions, or just have a poor grasp of IO operations!

See test code here:

use IO::Tee;
use strict;

my $tee = new IO::Tee(\*STDOUT, ">outfile.out");

#Test normal output
print $tee "normal data\n";

#Test system commands
my $cmdout = `dir /w`;
print $tee $cmdout."\n";

#Check input questions work
print $tee "Enter some data\n";
my $input = <>;
print $tee $input;

#Check stderr also goes to the file + screen.
warn "Warning here\n";
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Isn't it possible to redirect/reopen STDERR to STDOUT _before_ you call new IO::Tee ?

I don't think so - STDOUT doesn't go to the file -- it's the $tee filehandle that does the work... Need to direct STDERR to $tee, but my best guess, open (STDERR, ">$tee") doesn't work...