You should be able to inherit from Tie::Handle (part of the standard distribution) and override any methods you wish to define yourself: 
    package MySTDOUT;
    use Tie::Handle;
    @ISA = qw/Tie::Handle/;

    sub TIEHANDLE {
        my $class = shift;
        bless {}, $class;
    }

    package main;
    tie *STDOUT, 'MySTDOUT';

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For example, maybe you want to trap every call to STDOUT and prefix each argument with a string of your own: 
    package MySTDOUT;
    use Tie::Handle;
    @ISA = qw/Tie::Handle/;

    sub TIEHANDLE {
        my $class = shift;
        bless {}, $class;
    }

    sub PRINT {
        my $self = shift;
        my $caller = caller;
        print STDERR map "$caller: $_", @_;
    }

    package main;
    tie *STDOUT, 'MySTDOUT';

    print "Foo";

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Prints 
    main: Foo

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Take a look at the Apache module and Apache::Filter for some examples of tying STDOUT.

In reply to Re: monitor STDOUT in scalar by btrott
in thread monitor STDOUT in scalar by eak

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