I've written a goodly number of utilities over the years and in almost every case the core code is usually written with the output sent to STDOUT. As a long time fan of the 'tools' philosopy of K&R and 'nix in general this usually is a good solution. Except...well yes there is always an 'except' isn't there. As long as you apply the STDOUT solution one at a time, the problems are few-- but, as soon as you need to apply this to multiple input, then things get a little bit (sometimes more than a 'little') strained. As I'm facing just such a problem with my own code I thought I'd try and find a better approach with a small piece of perlish slight of hand.

To wit:

#!/perl/bin/perl
#
# wrap.pl -- proof of concept for wrapping a function tied to STDOUT, 
+such that you can tie it to whatever...
use strict;
no strict 'refs';
use warnings;
use diagnostics;
use IO::Scalar;
use SelectSaver;

for (map {glob $_} @ARGV) {
    my $s;

    wrapper((new IO::Scalar \$s),\&myFunction,$_);
    print "'$s'\n";
}

sub wrapper {
    my $saver = new SelectSaver(shift);

    &{$_[0]}($_[1]);
}

sub myFunction {
    my $filename = shift;

    print "\$filename = '$filename'\n";
    print <<'HERE';
template [name = "KeyValue"] (keyword,indent,value){
    Keyword(text = "concat($keyword,' =')",indent = "$indent")
    value-of("$value")
    text(";")
    Newline()
}
HERE
}
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–hsm

"Never try to teach a pig to sing…it wastes your time and it annoys the pig."